PFPT Proofpoint Inc

Filed by the Registrant ☒ Filed by a party other than the Registrant  ☐

Dear Proofpoint Stockholder:

You are cordially invited to attend a special meeting (including any adjournments or postponements thereof, the “Special Meeting”) of holders of common stock, par value $0.0001 per share, of Proofpoint, Inc. (“Proofpoint common stock,” and the holders thereof “Proofpoint Stockholders”), a Delaware corporation (“Proofpoint” or the “Company”), to be held on July 23, 2021, at 9:00 a.m., Pacific time. Due to public health concerns regarding the coronavirus (COVID-19) pandemic and to support the well-being of our employees and Proofpoint Stockholders, Proofpoint will hold the Special Meeting virtually via the Internet at www.virtualshareholdermeeting.com/PFPT2021SM. You will not be able to attend the Special Meeting physically in person. For purposes of attendance at the Special Meeting, all references in this proxy statement to “present in person” or “in person” shall mean virtually present at the Special Meeting.

At the Special Meeting, you will be asked to consider and vote on (i) a proposal to adopt the Agreement and Plan of Merger, dated as of April 25, 2021 (the “Merger Agreement”), by and among Proofpoint, Proofpoint Parent, LLC (f/k/a Project Kafka Parent, LLC), a Delaware limited liability company (“Parent”) and Project Kafka Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Merger Sub”), (ii) a proposal to approve, on an advisory (non-binding) basis, the compensation that may be paid or become payable to Proofpoint’s named executive officers that is based on or otherwise related to the Merger Agreement and the transactions contemplated by the Merger Agreement (the “Compensation Proposal”), and (iii) a proposal to adjourn the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting. Parent and Merger Sub are entities that are affiliated with Thoma Bravo, L.P., a private equity investment firm. All references herein to “Thoma Bravo” include Thoma Bravo, L.P. and the affiliated funds thereof. Pursuant to the terms of the Merger Agreement, Merger Sub will merge with and into Proofpoint and the separate corporate existence of Merger Sub will cease, with Proofpoint continuing as the surviving corporation and a wholly owned subsidiary of Parent (the “Merger”).

If the Merger is completed, you will be entitled to receive $176.00 in cash, less any applicable withholding taxes, for each share of Proofpoint common stock that you own, unless you have properly exercised your appraisal rights.

The Board of Directors of Proofpoint (the “Board of Directors”), after considering the factors more fully described in the enclosed proxy statement, has unanimously: (i) determined that it is in the best interests of Proofpoint and Proofpoint Stockholders, and declared it advisable, to enter into the Merger Agreement in accordance with the General Corporation Law of the State of Delaware (the “DGCL”) and consummate the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; (ii) approved the execution and delivery of the Merger Agreement by Proofpoint, the performance by Proofpoint of its covenants and other obligations under the Merger Agreement, and the consummation of the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; and (iii) resolved to recommend that Proofpoint Stockholders adopt the Merger Agreement in accordance with the DGCL. The Board of Directors unanimously recommends that you vote: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

The enclosed proxy statement provides detailed information about the Special Meeting, the Merger Agreement and the Merger. A copy of the Merger Agreement is attached as Annex A to the proxy statement.

The proxy statement also describes the actions and determinations of the Board of Directors in connection with its evaluation of the Merger Agreement and the Merger. You should carefully read and consider the entire enclosed proxy statement and its annexes, including, but not limited to, the Merger Agreement, as they contain important information about, among other things, the Merger and how it affects you.

Whether or not you plan to attend the Special Meeting in person, please sign, date and return, as promptly as possible, the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). If you attend the Special Meeting and vote in person by virtual ballot, your vote will revoke any proxy that you have previously submitted.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the proposal to adopt the Merger Agreement, without your instructions.

Your vote is very important, regardless of the number of shares that you own. We cannot complete the Merger unless the proposal to adopt the Merger Agreement is approved by the affirmative vote of the holders of at least a majority of the outstanding shares of Proofpoint common stock entitled to vote at the Special Meeting.

If you have any questions or need assistance voting your shares, please contact our proxy solicitor:

On behalf of the Board of Directors, I thank you for your support and appreciate your consideration of these matters.

The accompanying proxy statement is dated June 14, 2021 and, together with the enclosed form of proxy card, is first being mailed on or about June 14, 2021.

 

to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the proposal to adopt the Merger Agreement, without your instructions. If you sign, date and mail your proxy card without indicating how you wish to vote, your proxy will be counted as a vote “FOR” the adoption of the Merger Agreement, “FOR,” on an advisory (non-binding) basis, the Compensation Proposal and “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

WHETHER OR NOT YOU PLAN TO ATTEND THE SPECIAL MEETING IN PERSON, WE ENCOURAGE YOU TO SUBMIT YOUR PROXY AS PROMPTLY AS POSSIBLE: (1) BY TELEPHONE; (2) THROUGH THE INTERNET; OR (3) BY SIGNING AND DATING THE ENCLOSED PROXY CARD AND RETURNING IT IN THE POSTAGE-PAID ENVELOPE PROVIDED. You may revoke your proxy or change your vote at any time before it is voted at the Special Meeting.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your broker or other agent cannot vote on any of the proposals, including the proposal to adopt the Merger Agreement, without your instructions.

If you are a Proofpoint Stockholder of record, voting in person by virtual ballot at the Special Meeting will revoke any proxy that you previously submitted. If you hold your shares through a bank, broker or other nominee, you must obtain a “legal proxy” in order to vote in person at the Special Meeting.

If you fail to (1) return your proxy card, (2) grant your proxy electronically over the Internet or by telephone, or (3) vote by virtual ballot in person at the Special Meeting, your shares will not be counted for purposes of determining whether a quorum is present at the Special Meeting and, if a quorum is present, will have the same effect as a vote “AGAINST” the proposal to adopt the Merger Agreement but will have no effect on the Compensation Proposal or the adjournment proposal.

You should carefully read and consider the entire accompanying proxy statement and its annexes, including, but not limited to, the Merger Agreement, along with all of the documents incorporated by reference into the accompanying proxy statement, as they contain important information about, among other things, the Merger and how it affects you. If you have any questions concerning the Merger Agreement, the Merger, the Special Meeting or the accompanying proxy statement, would like additional copies of the accompanying proxy statement or need help voting your shares of Proofpoint common stock, please contact our proxy solicitor:

D.F. King & Co., Inc.

48 Wall Street, 22^nd Floor

New York, NY 10005

Banks and Brokers Call: (212) 269-5550

All Others Call: (866) 796-1271

Email: PFPT@dfking.com

The following questions and answers address some commonly asked questions regarding the Merger, the Merger Agreement and the Special Meeting. These questions and answers may not address all questions that are important to you. You should carefully read and consider the more detailed information contained elsewhere in this proxy statement and the annexes to this proxy statement, including, but not limited to, the Merger Agreement, along with all of the documents we refer to in this proxy statement, as they contain important information about, among other things, the Merger and how it affects you. You may obtain the information incorporated herein by reference without charge by following the instructions under the caption, “Where You Can Find More Information.”

Even if you plan to attend the Special Meeting in person, to ensure that your shares will be represented at the Special Meeting, we encourage you to sign, date and return the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). If you attend the Special Meeting and complete a virtual ballot, your vote will revoke any proxy previously submitted.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your broker or other agent cannot vote on any of the proposals, including the proposal to adopt the Merger Agreement, without your instructions. If you hold your shares in “street name,” you may not vote your shares in person at the Special Meeting unless you obtain a “legal proxy” from your bank, broker or other nominee.

Each Vested Company Option will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Vested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Vested Company Option, subject to any required withholding of taxes.

Each Unvested Company Option will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Unvested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Unvested Company Option. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company Option Consideration amounts will vest and become payable at the same time as the Company Option from which such Unvested Company Option Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company Option immediately prior to the Effective Time with respect to the receipt of the Unvested Company Option Consideration.

Each Vested Company RSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company RSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company RSU Consideration amounts will vest and become payable at the same time as the Company RSU from which such Unvested Company RSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company RSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company RSU Consideration.

Each Vested Company PSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Vested Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company PSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company PSU based on the attainment of the applicable performance metrics at the target level of

performance, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company PSU Consideration amounts will vest and be payable at the same time as the Company PSU from which such Unvested Company PSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Company PSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company PSU Consideration.

If a quorum is present at the Special Meeting, the failure of any Proofpoint Stockholder of record to: (i) submit a signed proxy card; (ii) grant a proxy over the Internet or by telephone (using the instructions provided in the enclosed proxy card); or (iii) vote in person by virtual ballot at the Special Meeting will have the same effect as a vote “AGAINST” the proposal to adopt the Merger Agreement. If you hold your shares in “street name” and a quorum is present at the Special Meeting, the failure to instruct your bank, broker or other nominee how to vote your shares will have the same effect as a vote “AGAINST” the proposal to adopt the Merger Agreement. If a quorum is present at the Special Meeting, abstentions will have the same effect as a vote “AGAINST” the proposal to adopt the Merger Agreement. Each “broker non-vote” will also count as a vote “AGAINST” the proposal to adopt the Merger Agreement but will have no effect on the Compensation Proposal or any proposal to adjourn the Special Meeting to a later date or dates to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting. If you properly sign your proxy card but do not mark the boxes showing how your shares should be voted on a matter, the shares represented by your properly signed proxy will be voted: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

Under specified circumstances, Proofpoint will be required to pay Parent a termination fee of either $122,982,000 or $368,946,000, upon the termination of the Merger Agreement, as described in the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Termination Fee.”

If your shares are held through a bank, broker or other nominee, you are considered the “beneficial owner” of shares of Proofpoint common stock held in “street name.” In that case, this proxy statement has been forwarded to you by your bank, broker or other nominee who is considered, with respect to those shares, to be the Proofpoint Stockholder of record. As the beneficial owner, you have the right to direct your bank, broker or other nominee how to vote your shares by following their instructions for voting. You are also invited to attend the Special Meeting. However, because you are not the Proofpoint Stockholder of record, you may not vote your shares in person at the Special Meeting unless you obtain a “legal proxy” from your bank, broker or other nominee.

A control number, located on your proxy card, is designed to verify your identity and allow you to vote your shares of Proofpoint common stock, and to confirm that your voting instructions have been properly recorded when voting electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). Please be aware that, although there is no charge for voting your shares, if you vote electronically over the Internet by visiting the address on your proxy card or by telephone by calling the phone number on your proxy card, in each case, you may incur costs such as Internet access and telephone charges for which you will be responsible.

Even if you plan to attend the Special Meeting in person, you are strongly encouraged to vote your shares of Proofpoint common stock by proxy. If you are a record holder or if you obtain a “legal proxy” to vote shares that you beneficially own, you may still vote your shares of Proofpoint common stock in person by virtual ballot at the Special Meeting even if you have previously voted by proxy. If you are present at the Special Meeting and vote in person by virtual ballot, your previous vote by proxy will not be counted.

If your shares are held in “street name” through a bank, broker or other nominee, you may vote through your bank, broker or other nominee by completing and returning the voting form provided by your bank, broker or other nominee, or, if such a service is provided by your bank, broker or other nominee,

electronically over the Internet or by telephone. To vote over the Internet or by telephone through your bank, broker or other nominee, you should follow the instructions on the voting form provided by your bank, broker or nominee.

If you hold your shares of Proofpoint common stock in “street name,” you should contact your bank, broker or other nominee for instructions regarding how to change your vote. You may also vote in person at the Special Meeting if you obtain a “legal proxy” from your bank, broker or other nominee.

If you properly sign your proxy card but do not mark the boxes showing how your shares should be voted on a matter, the shares represented by your properly signed proxy will be voted: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

You may receive more than one (1) set of voting materials, including multiple copies of this proxy statement and multiple proxy cards or voting instruction cards. For example, if you hold your shares in more than one (1) brokerage account, you will receive a separate voting instruction card for each brokerage account in which you hold shares. If you are a Proofpoint Stockholder of record and your shares are registered in more than one (1) name, you will receive more than one (1) proxy card.

For a more complete description of the U.S. federal income tax consequences of the Merger, see the section of this proxy statement captioned “The Merger—U.S. Federal Income Tax Consequences of the Merger.”

D.F. King & Co., Inc.

48 Wall Street, 22^nd Floor

New York, NY 10005

Banks and Brokers Call: (212) 269-5550

All Others Call: (866) 796-1271

Email: PFPT@dfking.com

This proxy statement, and any document to which Proofpoint refers in this proxy statement, contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 (the “Securities Act”), Section 21E of the Exchange Act and the Private Securities Litigation Reform Act of 1995, which are intended to be covered by the safe harbor created by such sections and other applicable laws. Such forward-looking statements include statements relating to Proofpoint’s strategy, goals, future focus areas and the value of the proposed transaction to Proofpoint Stockholders. These forward-looking statements are based on Proofpoint management’s beliefs and assumptions and on information currently available to management. Forward-looking statements include all statements that are not historical facts and may be identified by terms such as “expects,” “believes,” “plans,” or similar expressions and the negatives of those terms. These forward-looking statements involve known and unknown risks, uncertainties, and other factors that may cause actual results, performance or achievements to be materially different from any future results, performance or achievements, expressed or implied by the forward-looking statements, including the uncertainty associated with the potential impacts of the COVID-19 pandemic on Proofpoint’s business, financial condition, and results of operations. Additional factors that could cause or contribute to such differences include, but are not limited to, the following:

Proofpoint expressly qualifies in their entirety all forward-looking statements attributable to either Proofpoint or any person acting on Proofpoint’s behalf by the cautionary statements contained or referred to in this proxy statement. All information provided in this proxy statement is as of the date hereof and Proofpoint undertakes no duty to update this information except as required by law.

The enclosed proxy is solicited on behalf of the Board of Directors for use at the Special Meeting.

The Special Meeting will be held on July 23, 2021, at 9:00 a.m., Pacific time. Due to public health concerns regarding the coronavirus (COVID-19) pandemic and to support the well-being of our employees and Proofpoint Stockholders, Proofpoint will hold the special meeting virtually via the Internet at the virtual meeting website. You will not be able to attend the Special Meeting physically in person.

At the Special Meeting, we will ask Proofpoint Stockholders to vote on proposals to: (i) adopt the Merger Agreement; (ii) approve, on an advisory (non-binding) basis, the Compensation Proposal; and (iii) adjourn the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

Only Proofpoint Stockholders of record as of the Record Date are entitled to notice of the Special Meeting and to vote at the Special Meeting. A list of Proofpoint Stockholders entitled to vote at the Special Meeting will be available at the virtual meeting website during the Special Meeting. As of the Record Date, there were 57,627,801 shares of Proofpoint common stock outstanding and entitled to vote at the Special Meeting.

The holders of a majority of the stock issued and outstanding and entitled to vote in person or as represented by proxy will constitute a quorum at the Special Meeting. In the event that a quorum is not present at the Special Meeting, it is expected that the meeting will be adjourned to solicit additional proxies.

The affirmative vote of the holders of a majority of the outstanding shares of Proofpoint common stock is required to adopt the Merger Agreement. As of the Record Date, 28,813,901 votes constitute a majority of the outstanding shares of Proofpoint common stock. Adoption of the Merger Agreement by Proofpoint Stockholders is a condition to the closing of the Merger.

The affirmative vote by holders of a majority of the votes cast at the Special Meeting is required to approve, on an advisory (non-binding) basis, the Compensation Proposal.

Approval of the proposal to adjourn the Special Meeting, whether or not a quorum is present, requires the affirmative vote of a majority of votes cast at the Special Meeting.

If a Proofpoint Stockholder abstains from voting, that abstention will have the same effect as if Proofpoint Stockholders voted “AGAINST” the proposal to adopt the Merger Agreement, but will have no effect on the Compensation Proposal or any proposal to adjourn the Special Meeting to a later date or dates to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

Each “broker non-vote” will also count as a vote “AGAINST” the proposal to adopt the Merger Agreement but will have no effect on the Compensation Proposal or any proposal to adjourn the Special Meeting to a later date or dates to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting. A so-called “broker non-vote” results when banks, brokers and other nominees return a valid proxy voting upon a matter or matters for which the applicable rules provide discretionary authority but do not vote on a particular proposal because they do not have discretionary authority to vote on the matter and have not received specific voting instructions from the beneficial owner of such shares. Proofpoint does not expect any broker non-votes at the Special Meeting because the rules applicable to banks, brokers and other nominees only provide brokers with discretionary authority to vote on proposals that are considered routine, whereas each of the proposals to be presented at the Special Meeting is considered non-routine. As a result, no broker will be permitted to vote your shares of Proofpoint common stock at the Special Meeting without receiving instructions. Failure to instruct your broker on how to vote your shares will have the same effect as a vote “AGAINST” the proposal to adopt the Merger Agreement.

As of the Record Date, our directors and executive officers beneficially owned and were entitled to vote, in the aggregate, 797,392 shares of Proofpoint common stock, representing approximately 1.38% of the shares of Proofpoint common stock outstanding on the Record Date (and approximately 2.18% of the total shares of Proofpoint common stock outstanding when taking into account Company Options held, in the aggregate, by our directors and executive officers).

Our directors and executive officers have entered into the Voting Agreement with Parent and Proofpoint. Pursuant to the Voting Agreement, our directors and executive officers have agreed, among other things, to vote their shares of Proofpoint common stock in favor of the proposal to adopt and approve the Merger Agreement and against any competing transaction so long as the Merger Agreement has not been terminated and the Board of Directors has not made a Change of Recommendation. For more information, see the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—The Voting Agreement.”

If your shares are registered in your name with our transfer agent, Computershare, you may cause your shares to be voted by returning a signed and dated proxy card in the accompanying prepaid envelope, or you may vote in person at the Special Meeting. Additionally, you may grant a proxy electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). You must have the enclosed proxy card available and follow the instructions on the proxy card in order to grant a proxy electronically over the Internet or by telephone. Based on your proxy cards or Internet and telephone proxies, the proxy holders will vote your shares according to your directions.

If you plan to attend the Special Meeting and wish to vote in person, you will be given a virtual ballot at the Special Meeting. If your shares are registered in your name, you are encouraged to vote by proxy even if you plan to attend the Special Meeting in person. If you attend the Special Meeting and vote in person by virtual ballot, your vote will revoke any previously submitted proxy.

Voting instructions are included on your proxy card. All shares represented by properly signed and dated proxies received in time for the Special Meeting will be voted at the Special Meeting in accordance with the instructions of the Proofpoint Stockholder. Properly signed and dated proxies that do not contain voting instructions will be voted: (1) “FOR” adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

If your shares are held in “street name” through a bank, broker or other nominee, you may vote through your bank, broker or other nominee by completing and returning the voting form provided by your bank, broker or other nominee or attending the Special Meeting and voting in person with a “legal proxy” from your bank, broker or other nominee. If such a service is provided, you may vote over the Internet or telephone through your bank, broker or other nominee by following the instructions on the voting form provided by your bank, broker or other nominee. If you do not return your bank’s, broker’s or other nominee’s voting form, do not vote via the Internet or telephone through your bank, broker or other nominee, if possible, or do not attend the Special Meeting and vote in person with a “legal proxy” from your bank, broker or other nominee, it will have the same effect as if you voted “AGAINST” the proposal to adopt the Merger Agreement but will not have any effect on the Compensation Proposal or the adjournment proposal.

If you are a Proofpoint Stockholder of record, you may change your vote or revoke your proxy at any time before it is voted at the Special Meeting by:

If you have submitted a proxy, your appearance at the Special Meeting will not have the effect of revoking your prior proxy; provided that you do not vote in person or submit an additional proxy or revocation, which, in each case, will have the effect of revoking your proxy.

If you hold your shares of Proofpoint common stock in “street name,” you should contact your bank, broker or other nominee for instructions regarding how to change your vote. You may also vote in person at the Special Meeting if you obtain a “legal proxy” from your bank, broker or other nominee.

Any adjournment, postponement or other delay of the Special Meeting, including for the purpose of soliciting additional proxies, will allow Proofpoint Stockholders who have already sent in their proxies to revoke them at any time prior to their use at the Special Meeting as adjourned, postponed or delayed.

The Board of Directors has unanimously: (i) determined that it is in the best interests of Proofpoint and its Proofpoint Stockholders, and declared it advisable, to enter into the Merger Agreement in accordance with the DGCL and consummate the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; (ii) approved the execution and delivery of the Merger Agreement by Proofpoint, the performance by Proofpoint of its covenants and other obligations under the Merger Agreement, and the consummation of the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; and (iii) resolved to recommend that Proofpoint Stockholders adopt the Merger Agreement in accordance with the DGCL.

The Board of Directors unanimously recommends that you vote: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

The expenses of soliciting proxies will be paid by Proofpoint. Proofpoint has retained D.F. King & Co., Inc. to assist in soliciting proxies at a fee of $15,000, plus costs and expenses. Proofpoint and its agents may solicit proxies by mail, electronic mail, telephone, facsimile, by other similar means, or in person. Our directors, officers, and other employees, without additional compensation, and employees of D.F. King & Co., Inc. may solicit proxies personally or in writing, by telephone, email, or otherwise. Proofpoint will request brokers, custodians, nominees and other record holders to forward copies of the soliciting materials to persons for whom they hold shares and to request authority for the exercise of proxies. In such cases, Proofpoint, upon the request of the record holders, will reimburse such holders for their reasonable expenses. If you choose to access the proxy materials through the internet, you are responsible for any internet access charges you may incur.

Assuming timely satisfaction of necessary closing conditions, including the approval by Proofpoint Stockholders of the proposal to adopt the Merger Agreement, we anticipate that the Merger will be consummated in the third quarter of 2021.

If the Merger is consummated, Proofpoint Stockholders who continuously hold shares of Proofpoint common stock through the Effective Time, who do not vote in favor of the adoption of the Merger Agreement and who properly demand appraisal of their shares and do not withdraw their demands or otherwise lose their rights to seek appraisal will be entitled to seek appraisal of their shares in connection with the Merger under Section 262 of the DGCL. This means that Proofpoint Stockholders who perfect their appraisal rights, who do not thereafter withdraw their demand for appraisal, and who follow the procedures in the manner prescribed by Section 262 of the DGCL may be entitled to have their shares appraised by the Delaware Court of Chancery and to receive payment in cash of the “fair value” of their shares of Proofpoint common stock, exclusive of any elements of value arising from the accomplishment or expectation of the Merger, as determined by the Delaware Court of Chancery, together with interest to be paid on the amount determined to be “fair value,” if any, (or in certain circumstances described in further detail in the section of this proxy statement captioned “The Merger—Appraisal Rights,” on the difference between the amount determined to be the “fair value” and

the amount paid by the Surviving Corporation in the Merger to each Proofpoint Stockholder entitled to appraisal prior to the entry of judgment in any appraisal proceeding). Due to the complexity of the appraisal process, Proofpoint Stockholders who wish to seek appraisal of their shares are encouraged to review Section 262 of the DGCL carefully and to seek the advice of legal counsel with respect to the exercise of appraisal rights.

Stockholders considering seeking appraisal should be aware that the “fair value” of their shares as determined pursuant to Section 262 of the DGCL could be more than, the same as or less than the value of the Per Share Merger Consideration that they would receive pursuant to the Merger Agreement if they did not seek appraisal of their shares.

To exercise your appraisal rights, you must: (i) submit a written demand for appraisal to Proofpoint before the vote is taken on the proposal to adopt the Merger Agreement; (ii) not submit a proxy or otherwise vote in favor of the proposal to adopt the Merger Agreement; (iii) continue to hold your shares of Proofpoint common stock of record through the Effective Time; and (iv) strictly comply with all other procedures for exercising appraisal rights under Section 262 of the DGCL. Your failure to follow exactly the procedures specified under Section 262 of the DGCL may result in the loss of your appraisal rights. In addition, the Delaware Court of Chancery will dismiss appraisal proceedings in respect of the Merger unless certain stock ownership conditions are satisfied by Proofpoint Stockholders seeking appraisal. The DGCL requirements for exercising appraisal rights are described in further detail in the section of this proxy statement captioned “The Merger—Appraisal Rights,” which is qualified in its entirety by Section 262 of the DGCL, the relevant section of the DGCL regarding appraisal rights. A copy of Section 262 of the DGCL is reproduced and attached as Annex D to this proxy statement and incorporated herein by reference. If you hold your shares of Proofpoint common stock through a bank, brokerage firm or other nominee and you wish to exercise appraisal rights, you should consult with your bank, brokerage firm or other nominee to determine the appropriate procedures for the making of a demand for appraisal by such bank, brokerage firm or nominee.

If the Merger is completed, the shares of Proofpoint common stock will be delisted from NASDAQ and deregistered under the Exchange Act, and shares of Proofpoint common stock will no longer be publicly traded.

At this time, we know of no other matters to be voted on at the Special Meeting. If any other matters properly come before the Special Meeting, your shares of Proofpoint common stock will be voted in accordance with the discretion of the appointed proxy holders.

Unless we have received contrary instructions, we may send a single copy of this proxy statement to any household at which two (2) or more Proofpoint Stockholders reside if we believe Proofpoint Stockholders are members of the same family. Each Proofpoint Stockholder in the household will continue to receive a separate proxy card. This process, known as “householding,” reduces the volume of duplicate information received at your household and helps to reduce our expenses.

If you would like to receive your own set of our disclosure documents, please contact us using the instructions set forth below. Similarly, if you share an address with another Proofpoint Stockholder and together both of you would like to receive only a single set of our disclosure documents, please contact us using the instructions set forth below.

If you are a Proofpoint Stockholder of record, you may contact us by writing to Proofpoint at 925 West Maude Avenue, Sunnyvale, California 94085, or by calling Proofpoint at (408) 517-4710 and requesting to speak with our investor relations department. If a bank, broker or other nominee holds your shares, please contact your bank, broker or other nominee directly.

If you have any questions concerning the Merger, the Special Meeting or this proxy statement, would like additional copies of this proxy statement or need help voting your shares of Proofpoint common stock, please contact our proxy solicitor:

D.F. King & Co., Inc.

48 Wall Street, 22^nd Floor

New York, NY 10005

Banks and Brokers Call: (212) 269-5550

All Others Call: (866) 796-1271

Email: PFPT@dfking.com

This discussion of the Merger is qualified in its entirety by reference to the Merger Agreement, which is attached to this proxy statement as Annex A and incorporated into this proxy statement by reference. You should carefully read and consider the entire Merger Agreement, which is the legal document that governs the Merger, because this document contains important information about the Merger and how it affects you.

Proofpoint, Inc.

925 West Maude Avenue

Sunnyvale, California 94085

(408) 517-4710

Proofpoint is a leading next-generation cybersecurity company that enables primarily large and mid-sized organizations worldwide to protect the way their people work from advanced threats and compliance risks. Our integrated suite of products works together to help organizations build people-centric security and compliance programs. We provide threat protection, information protection, user protection, business ecosystem protection, and compliance solutions to address today’s rapidly changing threat and compliance landscape. Our solutions are built on a flexible, cloud-based platform and leverage proprietary technologies—including big data analytics, machine learning, deep content inspection, secure storage, advanced encryption, intelligent message routing, dynamic malware analysis, threat correlation, and virtual execution environments. We were founded in 2002 to provide a unified solution to help enterprises address their growing data security requirements. Proofpoint common stock is listed on NASDAQ under the symbol “PFPT.”

Proofpoint Parent, LLC (f/k/a Project Kafka Parent, LLC)

c/o Thoma Bravo, L.P.

600 Montgomery Street, 20th Floor

San Francisco, CA 94111

(415) 263-3600

Parent was formed on April 13, 2021, solely for the purpose of engaging in the transactions contemplated by the Merger Agreement, and has not engaged in any business activities other than in connection with the transactions contemplated by the Merger Agreement and arranging of the equity financing and debt financing in connection with the Merger.

Project Kafka Merger Sub, Inc.

c/o Thoma Bravo, L.P.

600 Montgomery Street, 20th Floor

San Francisco, CA 94111

(415) 263-3600

Merger Sub is a wholly owned subsidiary of Parent and was formed on April 13, 2021, solely for the purpose of engaging in the transactions contemplated by the Merger Agreement, and has not engaged in any business activities other than in connection with the transactions contemplated by the Merger Agreement and arranging of the equity financing and debt financing in connection with the Merger.

Parent and Merger Sub are each affiliated with the Thoma Bravo Funds, and Parent, Merger Sub and the Thoma Bravo Funds are each affiliated with Thoma Bravo. Thoma Bravo is a leading private equity firm focused on the software and technology-enabled services sectors. At the Effective Time, Surviving Corporation, will be indirectly owned by the Thoma Bravo Funds and certain of their affiliates.

In connection with the transactions contemplated by the Merger Agreement, (1) the Thoma Bravo Funds have provided Parent with an equity commitment and (2) Parent has obtained debt financing commitments from Goldman Sachs Bank USA. In addition, the Thoma Bravo Funds have agreed to guarantee the payment of certain liabilities and obligations of Parent or Merger Sub under the Merger Agreement, subject to an aggregate cap equal to $686.4 million, including any termination fee and amounts in respect of certain reimbursement and indemnification obligations of Parent and Merger Sub for certain costs, expenses or losses incurred or sustained by Proofpoint, as specified in the Merger Agreement. Such amounts will be used to fund the aggregate purchase

price required to be paid at the closing of the Merger and to also fund certain other payments (including the Required Amounts), subject to the terms and conditions of the Merger Agreement. For more information, please see the section of this proxy statement captioned “—Financing of the Merger.”

Upon the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into Proofpoint and the separate corporate existence of Merger Sub will cease, with Proofpoint continuing as the Surviving Corporation. As a result of the Merger, Proofpoint will become a wholly owned subsidiary of Parent, and Proofpoint common stock will no longer be publicly traded and will be delisted from NASDAQ. In addition, Proofpoint common stock will be deregistered under the Exchange Act, and we will no longer file periodic reports with the SEC. If the Merger is completed, you will not own any shares of the capital stock of the Surviving Corporation.

The Effective Time will occur upon the filing of a certificate of merger with the Secretary of State of the State of Delaware (or at such later time as we, Parent and Merger Sub may agree and specify in the certificate of merger).

If the Merger Agreement is not adopted by Proofpoint Stockholders, or if the Merger is not completed for any other reason:

At the Effective Time, each share of Proofpoint common stock (other than Excluded Shares, which include, for example, shares of Proofpoint common stock owned by Proofpoint Stockholders who have properly and validly exercised their statutory rights of appraisal in accordance with Section 262 of the DGCL) outstanding as of immediately prior to the Effective Time will be cancelled and automatically converted into the right to receive the Per Share Merger Consideration, less any applicable withholding taxes.

After the Merger is completed, you will have the right to receive the Per Share Merger Consideration in respect of each share of Proofpoint common stock that you own (less any applicable withholding taxes), but you will no longer have any rights as a Proofpoint Stockholder (except that Proofpoint Stockholders who properly exercise their appraisal rights will have a right to receive payment of the “fair value” of their shares as determined pursuant to an appraisal proceeding, as contemplated by Delaware law). For more information, please see the section of this proxy statement captioned “—Appraisal Rights.”

The Merger Agreement provides that Proofpoint’s equity awards that are outstanding immediately prior to the Effective Time will be subject to the following treatment as of the Effective Time:

Each Vested Company Option will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Vested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Vested Company Option, subject to any required withholding of taxes.

Each Unvested Company Option will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Unvested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Unvested Company Option. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company Option Consideration amounts will vest and become payable at the same time as the Company Option from which such Unvested Company Option Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company Option immediately prior to the Effective Time with respect to the receipt of the Unvested Company Option Consideration.

Each Vested Company RSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company RSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company RSU Consideration amounts will vest and become payable at the same time as the Company RSU from which such Unvested Company RSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company RSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company RSU Consideration.

Each Vested Company PSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Vested Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company PSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product

obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company PSU Consideration amounts will vest and be payable at the same time as the Company PSU from which such Unvested Company PSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company PSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company PSU Consideration.

In accordance with the terms of the Merger Agreement, on April 25, 2021, the Board of Directors adopted resolutions providing that with respect to the Company ESPP, (i) participation in the Company ESPP will be limited to those employees who are participants on the date of the Merger Agreement, (ii) participants may not increase their payroll deduction elections or rate of contributions from those in effect on the date of the Merger Agreement or make any separate non-payroll contributions to the Company ESPP on or following the date of the Merger Agreement, (iii) no offering period will be commenced after the date of the Merger Agreement, (iv) each then outstanding purchase right shall be exercised as of the earlier of (A) the end of the offering period in effect on the date of the Merger Agreement or (B) ten (10) days prior to the date on which the Effective Time occurs, and (v) the Company ESPP will terminate immediately prior to, but contingent upon the occurrence of, the Effective Time, but subsequent to the exercise of purchase rights on such purchase date (in accordance with the terms of the Company ESPP). On such exercise date, Proofpoint will apply the funds credited as of such date pursuant to the Company ESPP within each participant’s payroll withholding account to the purchase of whole shares of Proofpoint common stock in accordance with the terms of the Company ESPP and each share purchased thereunder immediately prior to the Effective Time will be canceled at the Effective Time and converted into the right to receive the Per Share Merger Consideration, subject to withholding of any applicable withholding taxes. Any accumulated contributions of each participant under the Company ESPP as of immediately prior to the Effective Time will, to the extent not used to purchase shares in accordance with the terms and conditions of the Company ESPP be refunded to such participant as promptly as practicable following the Effective Time (without interest).

As part of Proofpoint’s ongoing consideration and evaluation of its long-term strategic goals and plans, the Board of Directors and Proofpoint’s management periodically review, consider and assess Proofpoint’s operations and financial performance, as well as overall industry conditions, as they may affect those strategic goals and plans. This review includes, among other matters, the consideration of potential opportunities for business combinations, acquisitions and other financial and strategic alternatives.

On August 11, 2020, Mr. Andrew Almeida of Thoma Bravo contacted Mr. Gary Steele, CEO of Proofpoint to request a meeting.

On August 27, 2020, Messrs. Seth Boro and Chip Virnig of Thoma Bravo met with Mr. Steele and Mr. Jason Hurst, SVP of Corporate Development of Proofpoint, by videoconference. During the video conference, Messrs. Boro and Virnig discussed Thoma Bravo’s investment strategy as a general matter and the firm’s investments in software security businesses in particular. After some discussion, Mr. Boro stated that Thoma Bravo would be interested in exploring an acquisition of Proofpoint if Proofpoint was receptive to a potential transaction. Mr. Steele subsequently informed Dana Evan, the lead independent director of the Board of Directors of the foregoing conversation and they agreed to discuss Thoma Bravo’s interest with the Board of Directors at the next meeting of the board.

On October 27, 2020, the Proofpoint Board of Directors held its annual strategic planning meeting. The agenda included a comprehensive review of Proofpoint’s near term and long term business plans and strategies and the development of near term and long term financial projections. Mr. Steele informed the Board of Directors of his recent conversation with Messrs. Boro and Virnig and agreed to keep the Board of Directors apprised of any further discussions with Thoma Bravo.

On November 4, 2020, Messrs. Boro, Virnig and Almeida had another videoconference with Messrs. Steele and Hurst, during which Messrs. Boro, Virnig and Almeida previewed that they would be sending a written indication

of interest to acquire Proofpoint. Later that day, Proofpoint received a non-binding letter of intent from Thoma Bravo (the “Initial Letter of Intent”) to acquire Proofpoint for $125.00 per share in cash. The Initial Letter of Intent noted that the full consideration would be financed with a combination of equity from Thoma Bravo Funds and debt from one or more of Thoma Bravo’s lending partners, and the transaction would not be subject to a financing condition. The Initial Letter of Intent was promptly shared with the Board of Directors, with a note recommending that Proofpoint work with Morgan Stanley to evaluate the proposal and prepare an analysis for the Board of Directors. Proofpoint then contacted representatives of Morgan Stanley on November 4, 2020 to enlist their assistance with a review of Thoma Bravo’s proposal. Proofpoint requested Morgan Stanley’s assistance based on Proofpoint’s long standing relationship with Morgan Stanley, including Morgan Stanley’s work with Proofpoint in connection with its ongoing strategic review, as well as Morgan Stanley’s extensive expertise and experience advising software companies in connection with potential strategic transactions (including numerous transactions with Thoma Bravo). Proofpoint signed a formal engagement letter with Morgan Stanley on February 8, 2021.

On November 10, 2020, representatives of Morgan Stanley met with members of Proofpoint’s management team and reviewed information regarding Thoma Bravo’s past transaction behavior based on publicly available information. The following day, Mr. Steele spoke with Mr. Boro by telephone and informed Mr. Boro that Proofpoint would discuss Thoma Bravo’s Initial Letter of Intent at Proofpoint’s next board meeting.

On November 23, 2020, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden, Arps, Slate, Meagher & Flom LLP, Proofpoint’s outside counsel (“Skadden”), also attended the meeting. At the meeting, Mr. Steele outlined the terms of the Initial Letter of Intent and described his recent conversations with Messrs. Boro and Virnig. A representative of Skadden then provided an overview of the directors’ fiduciary duties in connection with their evaluation of a potential sale of Proofpoint in general and the proposal contained in the Initial Letter of Intent specifically. Representatives of Morgan Stanley then reviewed Morgan Stanley’s preliminary financial analysis of the proposal contained in the Initial Letter of Intent based on publicly available information. Morgan Stanley’s analysis included, among other things, the financial analysis of Proofpoint on a standalone basis, the premium and multiples implied by the proposal contained in the Initial Letter of Intent and Proofpoint’s potential vulnerability to activist shareholder attacks. The Board of Directors discussed the preliminary financial analysis of the proposal contained in the Initial Letter of Intent and determined that Proofpoint’s management team should continue its strategic review process and that a potential sale of Proofpoint for $125.00 per share in cash was not in the best interests of Proofpoint Stockholders and did not warrant further discussion or engagement with Thoma Bravo. The Board of Directors authorized Proofpoint’s management team to communicate the Board of Directors’ response to Thoma Bravo.

Later that day, Messrs. Steele and Hurst met with Messrs. Boro and Virnig by videoconference to provide feedback on the Initial Letter of Intent. Messrs. Steele and Hurst informed Messrs. Boro and Virnig that the Board of Directors and Proofpoint’s senior management were in the process of conducting a strategic review of Proofpoint’s business and the Board of Directors did not believe that the proposal contained in the Initial Letter of Intent was sufficient to interrupt Proofpoint’s strategic review. Mr. Steele emphasized that the Board of Directors and management were confident in Proofpoint’s business outlook and Proofpoint was not looking for a sale transaction. Despite this feedback, Messrs. Boro and Virnig suggested that representatives of Thoma Bravo and representatives of Proofpoint get together in January 2021 to discuss Thoma Bravo’s thoughts on Proofpoint and Thoma Bravo’s investment thesis underlying its interest in Proofpoint. Messrs. Boro and Virnig also suggested that Thoma Bravo might be able to improve its proposal with access to certain confidential information from Proofpoint, and, accordingly, they requested that the parties enter into a non-disclosure agreement to enable Proofpoint to provide this information to Thoma Bravo. Messrs. Steele and Hurst informed them, however, that Proofpoint was not interested in providing any confidential information to Thoma Bravo because Proofpoint was not looking for a sale transaction.

On November 24, 2020, a representative of Morgan Stanley received a call from Mr. Boro. On the call, Mr. Boro stated that Thoma Bravo was very interested in acquiring Proofpoint and believed that Thoma Bravo could make a compelling proposal with access to certain confidential information from Proofpoint. Mr. Boro emphasized that Thoma Bravo wanted to find a path forward with Proofpoint prior to the conclusion of Proofpoint’s strategic review so as not to lose time. The Morgan Stanley representative informed Mr. Boro that he would discuss the matter with Proofpoint management.

On November 25, 2020, Mr. Virnig contacted Mr. Steele to inform him that Thoma Bravo remained interested in a potential transaction with Proofpoint despite the Board of Directors' response and wanted to spend more time with Proofpoint’s management before the forthcoming holidays. Mr. Virnig also told Mr. Steele that he wanted to introduce him to Orlando Bravo, the founder of Thoma Bravo, so that Mr. Bravo could also explain Thoma Bravo’s interest in Proofpoint. On November 27, 2020, Mr. Steele informed Mr. Virnig that he was willing to meet with Mr. Bravo and would confirm his availability for a videoconference. Mr. Steele informed a member of the Board of Directors of this development in order to keep the Board of Directors generally advised of his engagement with Thoma Bravo.

On December 11, 2020, Messrs. Steele and Hurst met with a financial sponsor (“Financial Sponsor A”) to discuss a potential transaction with Proofpoint, following an introduction from a third party financial advisor.

On December 22, 2020, Messrs. Steele and Hurst met with Messrs. Virnig, Bravo and Boro by videoconference during which Messrs. Virnig, Bravo and Boro emphasized their continuing interest in acquiring Proofpoint and provided background on Thoma Bravo and some of its investments to date.

On January 22, 2021, members of Proofpoint’s management team provided Morgan Stanley with their forecasts of Proofpoint’s financial results based on their ongoing strategic review of Proofpoint’s business and their revised long range strategic plans for Proofpoint (the “Management Plan”).

On January 27, 2021, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Management presented a summary of the Management Plan and then representatives of Morgan Stanley reviewed Morgan Stanley’s updated preliminary financial analysis of the proposal contained in the Initial Letter of Intent based on publicly available information and the Management Plan. Morgan Stanley’s analysis included, among other things, the financial analysis of Proofpoint on a standalone basis, the premium and multiples implied by the proposal contained in the Initial Letter of Intent and Proofpoint’s potential vulnerability to activist shareholder attacks. After discussion, the Board of Directors maintained its previously reached determination that the proposal contained in Thoma Bravo’s Initial Letter of Intent was not in the best interests of Proofpoint Stockholders.

On February 1, 2021, Mr. Virnig again contacted Mr. Steele and requested a videoconference to discuss the progress of Proofpoint’s strategic review.

On February 5, 2021, Mr. Boro contacted a representative of Morgan Stanley to schedule a call. During the call, Mr. Boro reiterated Thoma Bravo’s interest in acquiring Proofpoint and expressed Thoma Bravo’s desire to find a path forward with Proofpoint. Mr. Boro requested guidance on a sale price that Proofpoint might find sufficiently attractive to warrant engagement. The representative of Morgan Stanley reiterated that, based on feedback and directions from Proofpoint, Proofpoint was not looking for a sale transaction so Thoma Bravo would likely need to propose a transaction reflecting a traditional market premium to Proofpoint’s then-current stock price to entice Proofpoint to engage in further discussions with Thoma Bravo.

On the morning of February 10, 2021, Mr. Boro also called Mr. Steele and a representative of Morgan Stanley to inform them that Thoma Bravo would be sending a revised written indication of interest to acquire Proofpoint. Following these telephone calls, Mr. Boro sent a revised non-binding letter of intent (the “First Revised Letter of Intent”) to Mr. Steele and representatives of Morgan Stanley. The First Revised Letter of Intent contained a proposal to acquire Proofpoint at $165.00 per share in cash, implying a premium of 25% to Proofpoint’s then-current stock price of $132.04.

On February 16, 2021, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Mr. Steele began by providing an update on his recent discussions with representatives of Thoma Bravo during which Messrs. Boro and Virnig continued to emphasize Thoma Bravo’s interest in Proofpoint. A representative of Skadden then reminded the Board of Directors of the directors’ fiduciary duties in connection with their evaluation of a potential sale transaction generally and the proposal contained in the First Revised Letter of Intent specifically. The representative of Skadden emphasized the importance of maintaining active board involvement and oversight over Proofpoint’s potential engagement with Thoma Bravo and other potential buyers. A representative of Morgan Stanley then led a discussion on Morgan Stanley’s preliminary financial analysis of the proposal contained in the First Revised Letter of Intent based in part on the Management Plan and then-prevailing market prices, including, among other things, a situational overview of Thoma Bravo’s recent interaction with

Proofpoint, a financial profile of the proposal contained in the First Revised Letter of Intent and a preliminary analysis of the proposal contained in the First Revised Letter of Intent in comparison to Proofpoint’s standalone intrinsic value implied by a variety of valuation analytics. The Board of Directors discussed potential responses to Thoma Bravo. Following such discussions, the Board of Directors directed representatives of Morgan Stanley to propose that Proofpoint would engage with Thoma Bravo if Thoma Bravo increased its proposed offer price to at least $175.00 per share in cash, but also directed Morgan Stanley to inform Thoma Bravo that Thoma Bravo would ultimately need to increase its offer price above $175.00 per share after completing its due diligence on Proofpoint in order to obtain the Board of Directors’ support for a transaction.

The Board of Directors then discussed whether to commence a market check to determine whether any third parties might have interest in exploring an acquisition of Proofpoint. As part of this discussion, representatives of Morgan Stanley described various structures and forms of market checks (including the use of a so-called “go-shop” arrangement) and the advantages and disadvantages of the various market check approaches, including the leak risks created by making outbound calls to a broad set of potential acquirors and the business risks created by contacting Proofpoint’s competitors to gauge their interest in acquiring Proofpoint. Morgan Stanley noted that Thoma Bravo’s proposal letters had expressed a willingness to incorporate a “go-shop” provision in any definitive agreement to acquire Proofpoint. Representatives of Morgan Stanley then reviewed an analysis of third parties who might have interest in exploring a potential acquisition of Proofpoint based on their financial resources and strategic fit with Proofpoint and suggested that Proofpoint contact three of these parties in a pre-signing market check. After discussion, the Board of Directors instructed representatives of Morgan Stanley and Proofpoint’s management team to contact three strategic buyers to assess their interest in acquiring Proofpoint. These strategic buyers are referred to herein as “Strategic Party A,” “Strategic Party B” and “Strategic Party C,” respectively. The Board of Directors determined not to contact other financial sponsors at that time based on the view that Thoma Bravo had unique expertise and interest in the security software business sector, coupled with its current willingness and financial capability to acquire a company of Proofpoint’s size and scale. The Board of Directors further noted that, if Proofpoint ultimately signed a definitive agreement with Thoma Bravo, it would be able to contact other financial sponsors during the “go-shop” process.

On February 17, 2021, as directed by the Board of Directors, a representative of Morgan Stanley called Mr. Boro by telephone and conveyed that the Board of Directors would not engage with Thoma Bravo on the terms of the proposal contained in the First Revised Letter of Intent, but would be prepared to share confidential information with Thoma Bravo and engage in a due diligence exercise more generally if Thoma Bravo increased its proposed price to $175.00 per share in cash. As directed by the Board of Directors, the representative of Morgan Stanley also emphasized that the Board of Directors expected that Thoma Bravo would ultimately need to pay more than $175.00 per share in cash in order to acquire Proofpoint. The representative of Morgan Stanley asked that Thoma Bravo submit a further revised proposal in writing. Later that night, Mr. Boro contacted a representative of Morgan Stanley and requested a copy of the Management Plan before determining whether it would be willing to increase its proposed offer price.

On February 18, 2021, representatives of Morgan Stanley called Paul Auvil, CFO of Proofpoint, by telephone, and after such discussion, it was agreed that Morgan Stanley would provide Thoma Bravo with the Morgan Stanley Equity Research report on Proofpoint and not the Management Plan on the basis that Thoma Bravo had not yet signed a non-disclosure agreement with Proofpoint. Later that day, a representative of Morgan Stanley sent to Mr. Boro the Morgan Stanley Equity Research report. The following day, Messrs. Steele and Auvil hosted a videoconference with Mr. Boro, other representatives of Thoma Bravo and representatives of Morgan Stanley to discuss Proofpoint’s long-term growth prospects, key areas of operational focus, and cash flow generation.

On February 21, 2021, Thoma Bravo sent Proofpoint a revised written non-binding letter of intent (the “Second Revised Letter of Intent”), which contained a revised proposal to acquire Proofpoint for $175.00 per share in cash, implying a premium of 26% to Proofpoint’s then-current stock price of $139.13. Later that day, a representative of Morgan Stanley requested that Thoma Bravo provide a summary work plan, and Thoma Bravo sent representatives of Morgan Stanley an outline of a work plan together with an initial ‘high priority’ due diligence request list.

On February 22, 2021, members of Proofpoint’s management and representatives of Thoma Bravo and Morgan Stanley met by videoconference to discuss initial matters related to the potential transaction, including dates for a management presentation and the initial due diligence request list and work plan provided by Thoma Bravo the previous day. During the videoconference, representatives of Thoma Bravo noted that the full consideration

would be financed with a combination of equity from Thoma Bravo Funds and debt from one of Thoma Bravo’s lending partners. The attendees agreed that a potential transaction could be executed in three weeks and that to meet this timeline, Thoma Bravo would send an agenda for management presentations and further due diligence request lists from its advisors over the next couple of days.

Later on February 22, 2021, Skadden shared a draft non-disclosure agreement with Thoma Bravo. The next day, Thoma Bravo shared with representatives of Morgan Stanley an agenda for a management presentation.

On February 25, 2021, representatives of Morgan Stanley met by videoconference with representatives of Thoma Bravo to discuss, among other items, the agenda for the management presentation to be held the following week.

On March 3, 2021, Proofpoint and Thoma Bravo signed a non-disclosure agreement that included a “standstill” provision (but did not include a so-called “don’t ask, don’t waive” provision).

On March 4, 2021, Messrs. Steele and Auvil hosted a management presentation by videoconference with Messrs. Boro, Virnig, Almeida and other representatives from Thoma Bravo and representatives of Morgan Stanley in attendance. At that meeting, Messrs. Steele and Auvil presented the Management Plan to Thoma Bravo and answered questions regarding the same.

On March 8, 2021, a representative of Morgan Stanley spoke with Mr. Boro by telephone and asked Mr. Boro to outline Thoma Bravo’s remaining due diligence requirements. Later that day, Thoma Bravo sent representatives of Morgan Stanley further due diligence requests from Thoma Bravo’s legal, financial and technology advisors.

On March 11, 2021, as authorized by Proofpoint, Morgan Stanley contacted Strategic Party A to inquire if it was interested in a potential acquisition of Proofpoint. Strategic Party A indicated that it was not interested in exploring a potential transaction with Proofpoint.

On March 14, 2021, Proofpoint hosted a financial due diligence kick-off meeting by videoconference, led by Mr. Auvil and Marlise Ricci, SVP and Corporate Controller of Proofpoint, with representatives of Thoma Bravo, Deloitte and Morgan Stanley in attendance.

On March 15, 2021, as authorized by Proofpoint, Morgan Stanley contacted Strategic Party B to inquire if it was interested in a potential acquisition of Proofpoint. Strategic Party B indicated that it was not interested in exploring a potential transaction with Proofpoint. Later that day, Mr. Steele contacted Strategic Party C to inquire if it was interested in a meeting in connection with a potential strategic transaction involving Proofpoint. Later that day, a representative of Strategic Party C introduced Mr. Steele to another member of Strategic Party C’s senior management team.

On March 16, 2021, Messrs. Steele and Auvil attended a dinner with Messrs. Boro, Virnig and another representative of Thoma Bravo during which the attendees discussed their respective visions for Proofpoint and Thoma Bravo’s investment thesis.

On March 17, 2021, Mr. Steele and other representatives of Proofpoint hosted a technology due diligence kick-off meeting by videoconference with representatives of Thoma Bravo, West Monroe Partners (“WMP”), Thoma Bravo’s technology advisor, and Morgan Stanley.

On March 19, 2021, Mr. Steele spoke by telephone with a representative of Strategic Party C to schedule a management presentation for Strategic Party C the following week.

On March 21, 2021, Mr. Auvil and Ms. Ricci hosted an accounting and financial due diligence meeting by videoconference with representatives of Thoma Bravo, Deloitte and Morgan Stanley. Later that day, a representative of Strategic Party C sent a draft non-disclosure agreement to a representative of Skadden. A representative of Skadden sent comments to a representative of Strategic Party C later that day.

On March 23, 2021, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Representatives of Morgan Stanley updated the Board of Directors on responses to Proofpoint’s outbound calls to Strategic Party A, B and C, noting that Morgan Stanley had contacted Strategic Party A and Strategic Party B, and Mr. Steele had contacted Strategic Party C. The representatives of Morgan Stanley reported that Strategic Party A and Strategic Party B had declined to engage, but that discussions with Strategic Party C were ongoing. The Board of Directors discussed potential outreach to two additional strategic buyers (referred to herein as “Strategic Party D” and “Strategic Party E”). The Board of Directors directed representatives of Morgan Stanley to contact

Strategic Party D, but declined to authorize calls to Strategic Party E at the time given competitive sensitivities with this party. The Board of Directors determined not to contact Strategic Party E unless and until there was already a strategic bidder for Proofpoint because Strategic Party E is a direct competitor and the Board of Directors believed that Strategic Party E was unlikely to engage unless there was other strategic interest in Proofpoint. The Board of Directors also considered the fact that any definitive agreement with Thoma Bravo was likely to include a “go-shop” provision that would allow Strategic Party E to pursue an acquisition of Proofpoint with a reduced termination fee if it was interested in acquiring Proofpoint.

On March 25, 2021, Proofpoint and Strategic Party C signed a non-disclosure agreement that included a “standstill” provision (but did not include a so-called “don’t ask, don’t waive” provision).

On March 29, 2021, as directed by Proofpoint, representatives of Morgan Stanley contacted Strategic Party D to inquire if such party was interested in a potential acquisition of Proofpoint. Strategic Party D indicated that it was not interested in exploring a potential transaction with Proofpoint. The following day, representatives of Proofpoint and Strategic Party C had a videoconference during which representatives of Proofpoint’s management team provided representatives of Strategic Party C with a management presentation.

On March 31, 2021, Mr. Steele and other members of Proofpoint's management hosted a technology/IT due diligence meeting by videoconference with representatives of Thoma Bravo, WMP and Morgan Stanley in attendance.

On April 2, 2021, a representative of Skadden sent a draft merger agreement to representatives of Kirkland & Ellis LLP, Thoma Bravo’s outside counsel (“Kirkland”), reflecting Proofpoint’s desired terms should Thoma Bravo determine to proceed with a transaction.

On April 4, 2021, Mr. Steele emailed Messrs. Boro and Virnig summarizing Proofpoint’s anticipated first quarter results and noting that the results were expected to beat equity research analyst expectations across a range of metrics including revenue, billings, bookings and free cash flow.

On April 5, 2021, representatives of Proofpoint hosted a follow-up management presentation with Strategic Party C by videoconference. Later that day, as directed by Proofpoint, representatives of Morgan Stanley provided access to the virtual data room to the financial advisor to Strategic Party C.

On April 9, 2021, members of Proofpoint’s management attended a videoconference with representatives of Thoma Bravo to discuss certain outstanding business diligence items.

On April 11, 2021, a representative of Kirkland sent a revised draft of the Merger Agreement to representatives of Skadden.

On April 13, 2021, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Mr. Steele updated the Board of Directors on his recent engagement with Thoma Bravo and key outstanding business diligence items. Messrs. Steele and Auvil previewed Proofpoint’s forthcoming first quarter results, due to be announced on April 29, 2021, which beat analysts’ consensus estimates. The Board of Directors asked Messrs. Steele and Auvil questions and discussed the forthcoming first quarter results, noting that it would be especially important, in light of these good results, to ensure that Proofpoint Stockholders received full value in any transaction with Thoma Bravo or any other buyer.

On April 14, 2021, Messrs. Steele and Auvil hosted a videoconference with Messrs. Boro and Virnig to discuss ongoing business due diligence. Later that day, members of Proofpoint’s management, including Mr. Steele, hosted a follow-up technology due diligence session by videoconference with WMP.

On April 16, 2021, Messrs. Steele and Auvil spoke with representatives of Thoma Bravo by telephone regarding Proofpoint’s outlook for the second quarter and remainder of 2021.

On April 17, 2021, a representative from Skadden sent a revised draft of the Merger Agreement to representatives of Kirkland.

On April 19, 2021, Thoma Bravo sent Proofpoint a letter (the “Third Revised Letter of Intent”) confirming the proposal contained in the Second Revised Letter of Intent to acquire Proofpoint at $175.00 per share in cash, implying a premium of 29% to Proofpoint’s then-current stock price of $135.62.

On April 20, 2021, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Mr. Steele informed the Board of Directors that Thoma Bravo had largely completed its due diligence on Proofpoint and had reaffirmed its previous proposal to acquire Proofpoint for $175.00 per share in cash. A representative of Morgan Stanley reminded the Board of Directors of Proofpoint’s recent outreach to other potential buyers, noting that none of them had expressed interest in exploring an acquisition of Proofpoint, other than Strategic Party C. Mr. Steele described his most recent conversations with representatives of Strategic Party C, noting that Strategic Party C had not sent an acquisition proposal nor shown the level of engagement that would suggest it was prepared to proactively pursue an acquisition of Proofpoint at such time. The Board of Directors agreed that Mr. Steele and Morgan Stanley should continue to provide assistance and support to Strategic Party C and agreed to consider the position again at the next meeting of the Board of Directors. Representatives of Morgan Stanley then reviewed Morgan Stanley’s updated financial analysis of Thoma Bravo’s proposal contained in the Third Revised Letter of Intent in comparison to Proofpoint’s standalone intrinsic value based on a variety of valuation methodologies, which discussion included, among other things, a financial profile of Thoma Bravo’s proposal contained in the Third Revised Letter of Intent and a preliminary analysis of Thoma Bravo’s proposal contained in the Third Revised Letter of Intent in comparison to Proofpoint’s standalone intrinsic value implied by a variety of valuation analytics. Following such discussion, the Board of Directors instructed the representatives of Morgan Stanley to inform Thoma Bravo that the Board of Directors would support a transaction at a price of $180.00 per share in cash. Later that day, representatives of Morgan Stanley presented the counterproposal to representatives of Thoma Bravo.

Later that day, a representative of Kirkland sent a revised draft of the Merger Agreement and drafts of the Voting Agreement, Equity Commitment Letter and Guaranty to representatives of Skadden.

On April 21, 2021, a representative of Thoma Bravo called a representative of Morgan Stanley by telephone and verbally presented Thoma Bravo’s “best and final offer” to acquire Proofpoint for $176.00 per share in cash (“Final Proposal”), implying a premium of 35% to Proofpoint’s then-current stock price of $130.75. Later that day a representative of Skadden sent a revised draft of the Merger Agreement to representatives of Kirkland.

On April 22, 2021, representatives of Skadden and Kirkland discussed the terms of the Merger Agreement by telephone. Later that day, a representative of Skadden sent revised drafts of the Voting Agreement, Equity Commitment Letter and Guaranty to representatives of Kirkland.

On April 23, 2021, a representative of Strategic Party C sent a note to Mr. Steele asking for a meeting, and Mr. Steele replied that he was available at Strategic Party C’s convenience. Later that day, a representative of Kirkland sent a revised draft of the Merger Agreement, Voting Agreement, Equity Commitment Letter and Guaranty to representatives of Skadden.

On April 24, 2021, a representative of Morgan Stanley sent a memorandum to representatives of Skadden, who in turn shared the memorandum with the Board of Directors disclosing certain relationships between Morgan Stanley on the one hand and Proofpoint and Thoma Bravo on the other hand (such memorandum, the “Relationship Disclosure”).

Later that day, the Board of Directors met by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. Prior to the representatives of Morgan Stanley entering the meeting, a representative of Skadden reviewed the Relationship Disclosure with the Board of Directors, and the Board of Directors determined that the relationships did not reflect a material conflict in the context of the proposed transaction. After such determination, the representatives of Morgan Stanley entered the meeting. A representative of Morgan Stanley reminded the Board of Directors that, at its last meeting, the Board of Directors had instructed Morgan Stanley to present a counteroffer of $180.00 per share in cash to Thoma Bravo and that Thoma Bravo had responded with its “best and final” offer of $176.00 per share in cash (implying a premium of 34% to Proofpoint’s then-current stock price of $131.78). Representatives of Morgan Stanley proceeded to outline the key terms of the proposal including: (1) a go-shop period of 45 days, (2) a termination fee equal to 1% of Proofpoint’s equity value based on the Per Share Merger Consideration payable by Proofpoint if Proofpoint terminated the Merger Agreement to enter into a definitive agreement in respect of a superior proposal with a party prior to the end of the go-shop period, (3) a termination fee equal to 3% of Proofpoint’s equity value based on the Per Share Merger Consideration payable by Proofpoint if Proofpoint terminated the Merger Agreement in certain circumstances, (4) a termination fee equal to 5.5% of Proofpoint’s

equity value based on the Per Share Merger Consideration payable by Thoma Bravo if Thoma Bravo terminated the Merger Agreement under certain circumstances, including if Thoma Bravo fails to secure financing for the transaction, and (5) key protections for employees. The Board of Directors discussed various aspects of Thoma Bravo’s Final Proposal, including agreeing that employee retention should be a key area of focus in order to allow Proofpoint to stabilize its employees during the pendency of the transaction given the likely uncertainties that the transaction would create. Mr. Steele provided an update on his conversations with Strategic Party C. At the meeting, the Board of Directors determined that Strategic Party C had been given sufficient time to indicate whether it was interested in tabling a proposal and that, in light of the lack of engagement to that date, it was unlikely that Strategic Party C would proceed. If Strategic Party C did decide to proceed, it would have the opportunity to do so during the “go-shop” period contemplated by the transaction with Thoma Bravo. After discussion, the Board of Directors concluded that, in light of all the factors and risks associated with Proofpoint’s standalone strategic plans and the pre-signing market check process, Thoma Bravo’s Final Proposal was in the best interests of Proofpoint Stockholders because, among a number of reasons, it enabled them to realize a significant premium for their stock without the execution and other risks associated with Proofpoint’s standalone strategic plans. The Board of Directors authorized and instructed Proofpoint’s management and representatives of Morgan Stanley to continue with negotiations with Thoma Bravo at $176.00 per share in cash and agreed to reconvene the following day to determine whether to finally approve the proposed transaction with Thoma Bravo. Later that day, Mr. Steele spoke with a representative of Strategic Party C by telephone and was informed that Strategic Party C had decided to terminate discussions with Proofpoint. Later that day, representatives of Skadden and Kirkland finalized drafts of the Voting Agreement, Equity Commitment Letter and Guaranty.

On April 25, 2021, the Board of Directors held a meeting by videoconference. Members of Proofpoint’s management team and representatives of Morgan Stanley and Skadden also attended the meeting. A representative of Morgan Stanley reviewed Morgan Stanley’s financial analysis of the transaction, including, among other things, the financial profile of Thoma Bravo’s final acquisition proposal, and an analysis of Thoma Bravo’s acquisition proposal in comparison to Proofpoint’s standalone intrinsic value implied by a variety of valuation analytics. A representative of Skadden then presented a detailed outline of the Merger Agreement, Voting Agreement, Equity Commitment Letter, Guaranty and Debt Commitment Letter that were envisioned to be signed concurrently with the Merger Agreement. After discussion among the Board of Directors and representatives of Skadden and Morgan Stanley, a representative of Morgan Stanley delivered Morgan Stanley’s oral opinion, subsequently confirmed in writing, dated April 25, 2021, to the Board of Directors that, as of such date and based upon and subject to the assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of review undertaken by Morgan Stanley as set forth in the written opinion, the Per Share Merger Consideration to be received by Proofpoint Stockholders (other than holders of the Excluded Shares) pursuant to the Merger Agreement was fair, from a financial point of view, to such Proofpoint Stockholders. After additional discussions of the proposed transaction and the matters summarized for the Board of Directors at the meeting, the Board of Directors unanimously (1) determined that it is in the best interests of Proofpoint and Proofpoint Stockholders, and declared it advisable, to enter into the Merger Agreement and consummate the Merger upon the terms and subject to the conditions set forth therein; (2) approved the Merger Agreement, the Merger, the other transactions contemplated by the Merger Agreement, the execution and delivery of the Merger Agreement by Proofpoint, the performance by Proofpoint of its covenants and other obligations thereunder, and the consummation of the Merger upon the terms and conditions set forth therein; and (3) resolved to recommend that Proofpoint Stockholders adopt the Merger Agreement in accordance with the DGCL.

Later in the evening that day, the parties executed and delivered the Merger Agreement, Voting Agreement, Equity Commitment Letter, Guaranty and Debt Commitment Letter.

Early in the morning on April 26, 2021, the parties issued a press release announcing the transaction.

From April 26, 2021, after the transaction was announced, and throughout the week of April 26, 2021, at the direction of the Board of Directors, representatives of Morgan Stanley contacted fifteen (15) strategic buyers and fourteen (14) financial sponsors regarding a potential acquisition of Proofpoint in connection with the go-shop provided for in the Merger Agreement.

On April 26, 2021, one other financial sponsor contacted representatives of Morgan Stanley about a potential acquisition of Proofpoint, but ultimately declined to move forward. Also on April 26, 2021, Strategic Party E reached out to representatives of Morgan Stanley about a potential acquisition of Proofpoint. The following day, on a telephone call with representatives of Morgan Stanley, a representative of Strategic Party E noted Strategic Party E was unlikely to be interested in a transaction.

On April 27, 2021, after an inquiry from representatives of Morgan Stanley, Financial Sponsor A indicated an interest in engaging in a potential acquisition of Proofpoint. The following day, a representative of Skadden sent to representatives of Financial Sponsor A a draft non-disclosure agreement by email.

On May 3, 2021, representatives of Skadden and Financial Sponsor A spoke by telephone call to discuss the non-disclosure agreement, and thereafter further traded emails on the same topic. Later that evening, a representative of Skadden sent an updated draft of the non-disclosure agreement to representatives of Financial Sponsor A.

On May 4, 2021, Proofpoint and Financial Sponsor A entered into a non-disclosure agreement. On May 5, 2021, pursuant to the Merger Agreement, a representative of Skadden notified representatives of Thoma Bravo and Kirkland that Proofpoint had entered into a non-disclosure agreement with a third party.

On May 6, 2021, members of Proofpoint’s management held a videoconference with representatives of Financial Sponsor A to discuss a potential transaction. On May 7, 2021, representatives of Financial Sponsor A spoke with representatives of Morgan Stanley by telephone call and noted that they were discussing whether Financial Sponsor A wanted to engage in a transaction.

On May 7, 2021, a representative of Strategic Party E confirmed to a representative of Proofpoint by telephone call that Strategic Party E would not participate in a potential transaction with Proofpoint.

On May 10, 2021, representatives of Financial Sponsor A requested certain diligence information about Proofpoint from representatives of Morgan Stanley by email. Later that day, as directed by Proofpoint, representatives of Morgan Stanley provided representatives of Financial Sponsor A with access to a virtual data room.

On May 17, 2021, representatives of Financial Sponsor A notified representatives of Morgan Stanley that Financial Sponsor A would not participate in a potential transaction with Proofpoint.

On June 9, 2021, at 11:59 p.m. Eastern time, the go-shop period provided for in the Merger Agreement expired. During the go-shop period, no party made an Alternative Acquisition Proposal.

The Board of Directors has unanimously: (i) determined that it is in the best interests of Proofpoint and Proofpoint Stockholders, and declared it advisable, to enter into the Merger Agreement in accordance with the DGCL and consummate the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; (ii) approved the execution and delivery of the Merger Agreement by Proofpoint, the performance by Proofpoint of its covenants and other obligations under the Merger Agreement, and the consummation of the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; and (iii) resolved to recommend that Proofpoint Stockholders adopt the Merger Agreement in accordance with the DGCL.

The Board of Directors unanimously recommends that you vote: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR,” on an advisory (non-binding) basis, the Compensation Proposal; and (3) “FOR” the adjournment of the Special Meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting.

In the course of reaching its determination and recommendation, the Board of Directors consulted with Proofpoint management, Skadden and Morgan Stanley. The Board of Directors considered a number of factors, including those below (which are not listed in any relative order of importance), all of which it viewed as generally supporting its (i) approval of the execution and delivery of the Merger Agreement by Proofpoint, the

performance by Proofpoint of its covenants and other obligations under the Merger Agreement, and the consummation of the Merger upon the terms and subject to the conditions set forth in the Merger Agreement; and (ii) resolution to recommend that Proofpoint Stockholders adopt the Merger Agreement in accordance with the DGCL:

The Board of Directors also considered a number of uncertainties and risks concerning the Merger, including the following (which factors are not necessarily presented in order of relative importance):

The foregoing discussion of reasons for the recommendation to adopt the Merger Agreement is not meant to be exhaustive but addresses the material information and factors considered by the Board of Directors in consideration of its recommendation. In view of the wide variety of factors considered by the Board of Directors in connection with its evaluation of the Merger and the complexity of these matters, the Board of Directors did not find it practicable to, and did not, quantify or otherwise assign relative weights to the specific factors considered in reaching its determination and recommendation. Rather, in considering the information and factors described above, individual members of the Board of Directors each applied his or her own personal business judgment to the process and may have given differing weights to differing factors. The Board of Directors based its unanimous recommendation on the totality of the information presented. The explanation of the factors and reasoning set forth above contain forward-looking statements that should be read in conjunction with the section of this proxy statement captioned “Forward-Looking Statements.”

Proofpoint retained Morgan Stanley to provide it with financial advisory services and a financial opinion in connection with the possible sale of Proofpoint. The Board of Directors selected Morgan Stanley to act as its financial advisor based on Morgan Stanley’s qualifications, expertise and reputation, its knowledge of and involvement in recent transactions in Proofpoint’s industry, its knowledge of Proofpoint’s business and affairs and its understanding of Proofpoint’s business based on its long-standing relationship with Proofpoint. At the meeting of the Board of Directors on April 25, 2021, Morgan Stanley rendered its oral opinion, subsequently confirmed in writing, that, as of April 25, 2021, and based upon and subject to the assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of review undertaken by Morgan Stanley as set forth in the written opinion, the Per Share Merger Consideration to be received by Proofpoint Stockholders (other than the holders of the Excluded Shares) pursuant to the Merger Agreement was fair from a financial point of view to such Proofpoint Stockholders.

The full text of the written opinion of Morgan Stanley, dated as of April 25, 2021, which sets forth, among other things, the assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of the review undertaken by Morgan Stanley in rendering its opinion, is attached to this proxy statement as Annex C and incorporated by reference in this proxy statement in its entirety. The summary of the opinion of Morgan Stanley in this proxy statement is qualified in its entirety by reference to the full text of the opinion. You are encouraged to read Morgan Stanley’s opinion carefully and in its entirety. Morgan Stanley’s opinion was directed to the Board of Directors, in its capacity as such, and addresses only the fairness from a financial point of view of the Per Share Merger Consideration to be received by Proofpoint Stockholders (other than the holders of the Excluded Shares) pursuant to the Merger Agreement as of the date of the opinion and does not address the relative merits of the Merger as compared to any other alternative business transaction, or other alternatives, or whether or not such alternatives could be achieved or are available. It was not intended to, and does not, constitute an opinion or a recommendation as to how Proofpoint Stockholders should vote at the Special Meeting. The summary of the opinion of Morgan Stanley set forth below is qualified in its entirety by reference to the full text of the opinion.

In connection with rendering its opinion, Morgan Stanley, among other things:

In arriving at its opinion, Morgan Stanley assumed and relied upon, without independent verification, the accuracy and completeness of the information that was publicly available or supplied or otherwise made available to Morgan Stanley by Proofpoint, and formed a substantial basis for its opinion. With respect to the Management Projections, Morgan Stanley assumed that they had been reasonably prepared on bases reflecting the best currently available estimates and judgments of Proofpoint’s management of the future financial performance of Proofpoint. Morgan Stanley expressed no view as to such Management Projections or the assumptions on which they were based. In addition, Morgan Stanley assumed that the Merger will be consummated in accordance with the terms set forth in the Merger Agreement without any waiver, amendment or delay of any terms or conditions, including among other things, that Parent will obtain financing in accordance with the terms set forth in the Financing Letters, and that the definitive Merger Agreement would not differ in any material respect from the draft thereof furnished to Morgan Stanley. Morgan Stanley assumed that, in connection with the receipt of all the necessary governmental, regulatory or other approvals and consents required for the proposed merger, no delays, limitations, conditions or restrictions will be imposed that would have a material adverse effect on the contemplated benefits expected to be derived in the proposed merger. Morgan Stanley is not a legal, tax or regulatory advisor. Morgan Stanley is a financial advisor only and relied upon, without independent verification, the assessment of Proofpoint and its legal, tax or regulatory advisors with respect to legal, tax or regulatory matters. Morgan Stanley’s opinion does not address the relative merits of the Merger as compared to any other alternative business transaction, or other alternatives, or whether or not such alternatives could be achieved or are available. Morgan Stanley expressed no opinion with respect to the fairness of the amount or nature of the compensation to any of Proofpoint’s officers, directors or employees, or any class of such persons, relative to the Per Share Merger Consideration to be received by Proofpoint Stockholders (other than the holders of the Excluded Shares) in the Merger. Morgan Stanley did not make any independent valuation or appraisal of the assets or liabilities of Proofpoint, nor was Morgan Stanley furnished with any such valuations or appraisals. Morgan Stanley’s opinion was necessarily based on financial, economic, market and other conditions as in effect on, and the information made available to Morgan Stanley as of, April 25, 2021. Events occurring after April 25, 2021, may affect Morgan Stanley’s opinion and the assumptions used in preparing it, and Morgan Stanley has not assumed any obligation to update, revise or reaffirm its opinion.

The following is a brief summary of the material analyses performed by Morgan Stanley in connection with its oral opinion and the preparation of its written opinion letter dated as of April 25, 2021, to the Board of Directors. The following summary is not a complete description of Morgan Stanley’s opinion or the financial analyses performed and factors considered by Morgan Stanley in connection with its opinion, nor does the order

of analyses described represent the relative importance or weight given to those analyses. Some of these summaries of financial analyses include information presented in tabular format. In order to fully understand the financial analyses used by Morgan Stanley, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The analyses listed in the tables and described below must be considered as a whole; considering any portion of such analyses and the factors considered, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Morgan Stanley’s opinion.

In performing the financial analyses summarized below and in arriving at its opinion, Morgan Stanley utilized and relied upon (i) the Management Plan and (ii) the consensus estimates of equity research analysts (the “Street Consensus”). The Management Plan is more fully described below in the section of this proxy statement captioned “—Management Projections.” In accordance with direction from the Board of Directors, Morgan Stanley utilized the Street Consensus and Management Plan in its financial analyses described below.

Morgan Stanley performed a public trading comparables analysis, which attempts to provide an implied value of a company by comparing it to similar companies that are publicly traded. Morgan Stanley reviewed and compared certain financial estimates for Proofpoint with comparable publicly available consensus equity analyst research estimates for companies, selected based on Morgan Stanley’s professional judgment and experience, that share similar business characteristics and have certain comparable operating characteristics including, among other things, similarly sized revenue and/or revenue growth rates, market capitalizations, profitability, scale and/or other similar operating characteristics (these companies are referred to as the “comparable companies”). These companies were the following:

For purposes of this analysis, Morgan Stanley analyzed the ratio of fully diluted equity value to estimated levered free cash flow (“LFCF”), which, for purposes of this analysis, (i) for Proofpoint, (x) was provided to Morgan Stanley, and approved for Morgan Stanley’s use, by Proofpoint’s management for calendar years 2021 and 2022 for the Management Plan, and (y) was based on publicly available consensus equity analyst research estimates for calendar years 2021 and 2022 for the Street Consensus; and (ii) for each of the comparable companies, was based on publicly available consensus equity analyst research estimates for comparison purposes. Based on its analysis of the relevant metrics for each of the comparable companies and upon the application of its professional judgment and experience, Morgan Stanley selected representative ranges of fully diluted equity value to LFCF multiples and applied these ranges of multiples to the estimated relevant metric for Proofpoint. For purposes of this analysis, Morgan Stanley utilized publicly available financial information, available as of April 23, 2021 (the last full trading day prior to the meeting of the Board of Directors to approve and adopt the Merger Agreement, declare the advisability of the Merger Agreement and approve the transactions contemplated thereby, including the Merger).

Based on the outstanding shares of Proofpoint common stock on a fully diluted basis as provided by Proofpoint’s management and the selected ranges of fully diluted equity value to LFCF, Morgan Stanley calculated the estimated implied value per share of Proofpoint common stock as follows:

No company utilized in the public trading comparables analysis is identical to Proofpoint. In evaluating the comparable companies, Morgan Stanley made numerous assumptions with respect to industry performance, general business, regulatory, economic, market and financial conditions and other matters, many of which are beyond Proofpoint’s control. These include, among other things, the impact of competition on Proofpoint’s business and the industry generally, industry growth, and the absence of any adverse material change in the financial condition and prospects of Proofpoint and the industry, and in the financial markets in general. Mathematical analysis (such as determining the average or median) is not in itself a meaningful method of using comparable company data.

Morgan Stanley performed a discounted equity value analysis, which is designed to provide insight into the potential future equity value of a company as a function of such company’s estimated future LFCF. The resulting equity value is subsequently discounted to arrive at an estimate of the implied present value. In connection with this analysis, Morgan Stanley calculated a range of implied present equity values per share of the Proofpoint common stock on a standalone basis for each of the Street Consensus and Management Plan.

To calculate these discounted fully diluted equity values, Morgan Stanley utilized calendar year 2023 LFCF estimates under each of the Street Consensus and Management Plan. Based upon the application of its professional judgment and experience, Morgan Stanley applied a forward range of fully diluted equity value to LFCF multiples (based on the range of fully diluted equity value to LFCF multiples for the comparable companies) to these LFCF estimates in order to reach a future implied fully diluted equity value.

In each case, Morgan Stanley then discounted the resulting implied future fully diluted equity value to April 23, 2021, at a discount rate of 8.1%, which rate was selected based on Proofpoint’s estimated cost of equity, which was arrived at by applying the capital asset pricing model, to calculate the discounted fully diluted equity value. The resulting discounted fully diluted equity value was then divided by Proofpoint’s fully diluted share count as provided by Proofpoint’s management to derive the implied discounted fully diluted equity value per share as follows:

Morgan Stanley performed a discounted cash flow analysis, which is designed to provide an implied value of a company by calculating the present value of the estimated future cash flows and terminal value of such company. Morgan Stanley calculated a range of fully diluted equity values per share for the Proofpoint common stock based on a discounted cash flow analysis to value Proofpoint as a standalone entity. Morgan Stanley utilized estimates from the Street Consensus and Management Plan for purposes of its discounted cash flow analysis, as more fully described below.

Morgan Stanley first calculated the estimated unlevered free cash flow, which is defined as non-GAAP operating income, plus depreciation and amortization expense, less (1) stock-based compensation expense, (2) cash taxes,

(3) capital expenditures, and (4) capitalized software expense and plus or minus changes in net working capital and other adjustments. Each of the Street Consensus and Management Plan included estimates prepared by Proofpoint’s management through 2030. The free cash flows and terminal values were discounted, using a mid-year convention, to present values as of April 23, 2021, at a discount rate ranging from 7.1% to 9.0%, which discount rates were selected, upon the application of Morgan Stanley’s professional judgment and experience, to reflect an estimate of Proofpoint’s weighted average cost of capital determined by the application of the capital asset pricing model.

Based on the outstanding shares of Proofpoint common stock on a fully diluted basis as provided by Proofpoint’s management, Morgan Stanley calculated the estimated implied value per share of Proofpoint common stock as follows:

Morgan Stanley performed a precedent transactions multiples analysis, which is designed to imply a value of a company based on publicly available financial terms. Morgan Stanley compared publicly available statistics for selected software transactions. Morgan Stanley selected such comparable transactions because they shared certain characteristics with the Merger, most notably because they were similar software transactions. For such transactions, Morgan Stanley noted the estimated fully diluted equity value of the transaction to the next 12 months’ (which we refer to as “NTM”) LFCF based on publicly available information at the time of announcement of each such transaction.

The following is a list of the selected software transactions reviewed, together with the applicable multiples:

Based on its analysis of the relevant metrics and time frame for each of the transactions listed above and upon the application of its professional judgment and experience, Morgan Stanley selected representative ranges of the fully diluted equity value to the estimated NTM LFCF multiples of the transactions, and applied these ranges of multiples to the estimated calendar year 2021 LFCF for Proofpoint based on the Management Plan and the Street Consensus. The following table summarizes Morgan Stanley’s analysis:

No company or transaction utilized in the precedent transactions analysis is identical to Proofpoint or the Merger. In evaluating the precedent transactions, Morgan Stanley made numerous assumptions with respect to industry performance, general business, regulatory, economic, market and financial conditions and other matters, many of

which are beyond Proofpoint’s control. These include, among other things, the impact of competition on Proofpoint’s business and the industry generally, industry growth, and the absence of any adverse material change in the financial condition and prospects of Proofpoint and the industry, and in the financial markets in general, which could affect the public trading value of the companies and the aggregate value and fully diluted equity value of the transactions to which they are being compared. The fact that points in the range of implied present value per share of Proofpoint derived from the valuation of precedent transactions were less than or greater than the Per Share Merger Consideration is not necessarily dispositive in connection with Morgan Stanley’s analysis of the consideration for the Merger, but is one of many factors Morgan Stanley considered.

Morgan Stanley performed an illustrative precedent premiums analysis by reviewing the same sets of comparable transactions as under the Precedent Transactions Multiples Analysis. For these transactions, Morgan Stanley noted the distributions of the implied premium to the acquired company’s closing share price on the last trading day prior to announcement (or the last trading day prior to the share price being affected by acquisition rumors or similar news). The following table summarizes Morgan Stanley’s analysis:

Based on its analysis of the premia for such transactions and based upon the application of its professional judgment and experience, Morgan Stanley selected a representative range of premia and applied such range to Proofpoint’s closing share price on April 23, 2021 (the last full trading day prior to the meeting of the Board of Directors to approve and adopt the Merger Agreement, declare the advisability of the Merger Agreement and approve the transactions contemplated thereby, including the Merger).

The following table summarizes such calculation:

Morgan Stanley noted certain future public market trading price targets for Proofpoint common stock prepared and published by equity research analysts prior to April 23, 2021 (the last full trading day prior to the meeting of the Board of Directors to approve and adopt the Merger Agreement, declare the advisability of the Merger Agreement and approve the transactions contemplated thereby, including the Merger). These targets reflected each analyst’s estimate of the future public market trading price of Proofpoint common stock. The range of undiscounted analyst price targets for the Proofpoint common stock was $100 to $166 per share as of various dates ranging from November 1, 2020 to April 18, 2021. Morgan Stanley discounted the range of analyst price targets per share for the Proofpoint common stock by one year at a rate of 8.1%, which discount rate was selected by Morgan Stanley, upon the application of its professional judgment and experience, to reflect Proofpoint’s cost of equity. This analysis indicated an implied range of fully diluted equity values for Proofpoint common stock of $92 to $154 per share, as discounted by one year based on undiscounted analyst price targets, as of April 23, 2021 (the last full trading day prior to the meeting of the Board of Directors to approve and adopt the Merger Agreement, declare the advisability of the Merger Agreement and approve the transactions contemplated thereby, including the Merger).

The public market trading price targets published by equity research analysts do not necessarily reflect current market trading prices for Proofpoint common stock, and these estimates are subject to uncertainties, including the future financial performance of Proofpoint and future financial market conditions.

In connection with the review of the Merger by the Board of Directors, Morgan Stanley performed a variety of financial and comparative analyses for purposes of rendering its opinion. The preparation of a financial opinion is a complex process and is not necessarily susceptible to a partial analysis or summary description. In arriving at its opinion, Morgan Stanley considered the results of all of its analyses as a whole and did not attribute any particular weight to any analysis or factor it considered. Morgan Stanley believes that selecting any portion of its analyses, without considering all analyses as a whole, would create an incomplete view of the process underlying its analyses and opinion. In addition, Morgan Stanley may have given various analyses and factors more or less weight than other analyses and factors, and may have deemed various assumptions more or less probable than other assumptions. As a result, the ranges of valuations resulting from any particular analysis described above should not be taken to be Morgan Stanley’s view of the actual value of Proofpoint. In performing its analyses, Morgan Stanley made numerous assumptions with respect to industry performance, general business, regulatory, economic, market and financial conditions and other matters, many of which are beyond Proofpoint’s control. These include, among other things, the impact of competition on Proofpoint’s business and the industry generally, industry growth, and the absence of any adverse material change in the financial condition and prospects of Proofpoint and the industry, and in the financial markets in general. Any estimates contained in Morgan Stanley’s analyses are not necessarily indicative of future results or actual values, which may be significantly more or less favorable than those suggested by such estimates.

Morgan Stanley conducted the analyses described above solely as part of its analysis of the fairness from a financial point of view of the Per Share Merger Consideration to be received by Proofpoint Stockholders (other than the holders of the Excluded Shares) pursuant to the Merger Agreement and in connection with the delivery

of its opinion dated as of April 25, 2021 to the Board of Directors. These analyses do not purport to be appraisals or to reflect the prices at which shares of Proofpoint common stock might actually trade.

The Per Share Merger Consideration to be received by Proofpoint Stockholders (other than the holders of the Excluded Shares) pursuant to the Merger Agreement was determined through arm’s-length negotiations between Proofpoint and Parent and was approved by the Board of Directors. Morgan Stanley provided advice to the Board of Directors during these negotiations but did not, however, recommend any specific consideration to Proofpoint or the Board of Directors, nor did Morgan Stanley opine that any specific consideration constituted the only appropriate consideration for the Merger. Morgan Stanley’s opinion did not address the relative merits of the Merger as compared to any other alternative business transaction, or other alternatives, or whether or not such alternatives could be achieved or are available. Morgan Stanley’s opinion was not intended to, and does not, constitute an opinion or a recommendation as to how Proofpoint Stockholders should vote at the Special Meeting.

Morgan Stanley’s opinion and its presentation to the Board of Directors was one of many factors taken into consideration by the Board of Directors to approve and adopt the Merger Agreement. Consequently, the analyses as described above should not be viewed as determinative of the opinion of the Board of Directors with respect to the consideration pursuant to the Merger Agreement or of whether the Board of Directors would have been willing to agree to a different consideration. Morgan Stanley’s opinion was approved by a committee of Morgan Stanley investment banking and other professionals in accordance with Morgan Stanley’s customary practice.

The Board of Directors retained Morgan Stanley based upon Morgan Stanley’s qualifications, experience and expertise. Morgan Stanley is a global financial services firm engaged in the securities, investment management and individual wealth management businesses. Its securities business is engaged in securities underwriting, trading and brokerage activities, foreign exchange, commodities and derivatives trading, prime brokerage, as well as providing investment banking, financing and financial advisory services. Morgan Stanley, its affiliates, directors and officers may at any time invest on a principal basis or manage funds that invest, hold long or short positions, finance positions, and may trade or otherwise structure and effect transactions, for their own account or the accounts of their customers, in debt or equity securities or loans of Proofpoint, Parent, Thoma Bravo and their respective affiliates, or any other company, or any currency or commodity, that may be involved in the Merger, or any related derivative instrument.

Under the terms of its engagement letter, Morgan Stanley provided Proofpoint financial advisory services and an opinion, described in this section and attached to this proxy statement as Annex C, in connection with the Merger, and Proofpoint has agreed to pay Morgan Stanley a fee of approximately $78 million for its services, $16 million of which has been paid following delivery of the opinion described in this section and attached to this proxy statement as Annex C and the remainder of which is contingent upon the consummation of the Merger. Proofpoint has also agreed to reimburse Morgan Stanley for its expenses, including fees of outside counsel and other professional advisors, incurred in connection with its engagement. In addition, Proofpoint has agreed to indemnify Morgan Stanley and its affiliates, its and their respective officers, directors, employees and agents and each other person, if any, controlling Morgan Stanley or any of its affiliates against certain liabilities and expenses related to, arising out of or in connection with Morgan Stanley’s engagement, including certain liabilities under the federal securities laws.

In the two years prior to the date of Morgan Stanley’s opinion, Morgan Stanley and its affiliates have provided financing services for Proofpoint and received aggregate fees of approximately $5 to $10 million in connection with such services. In the two years prior to the date of Morgan Stanley’s opinion, Morgan Stanley and its affiliates have provided financial advisory and financing services for Thoma Bravo and certain of its affiliates and their affiliated funds’ respective portfolio companies (collectively, the “Thoma Bravo Related Entities”), and have received aggregate fees of approximately $20 to $40 million in connection with such services. Morgan Stanley may also seek to provide financial advisory and financing services to Proofpoint and Thoma Bravo Related Entities and their respective affiliates in the future and would expect to receive fees for the rendering of these services.

On August 20, 2019, in connection with the pricing of the Convertible Notes, Proofpoint entered into privately negotiated capped call transactions (the “Base Capped Call Transactions”) with each of Morgan Stanley & Co. LLC, Bank of America, N.A., Citibank, N.A., and Wells Fargo Bank, National Association or their respective

affiliates (the “Capped Call Counterparties”). On August 21, 2019, in connection with the initial purchasers’ exercise of their option to purchase additional Convertible Notes, Proofpoint entered into additional capped call transactions with the Capped Call Counterparties (the “Additional Capped Call Transactions” and, together with the Base Capped Call Transactions the “Capped Call Transactions”). The Capped Call Transactions initially covered, subject to customary anti-dilution adjustments, the number of shares of Proofpoint common stock that initially underlie the Convertible Notes. The strike price of the Capped Call Transactions is $153.99 per share of Proofpoint common stock, and the cap price of the Capped Call Transactions is $223.98 per share of Proofpoint common stock, and is subject to certain adjustments under the terms of the Capped Call Transactions. The Capped Call Transactions are expected generally to reduce potential dilution to Proofpoint Stockholders upon conversion of the Convertible Notes and/or offset the potential cash payments that Proofpoint could be required to make in excess of the principal amount of any converted Convertible Notes upon conversion thereof, with such reduction and/or offset subject to a cap based on the cap price.

If the Merger is consummated, holders of the Convertible Notes may convert their Convertible Notes, which would result in termination of the Capped Call Transactions. Under the terms of the documents governing the Capped Call Transactions, each Capped Call Counterparty would be obligated to pay Proofpoint the “fair value” of the transaction, determined pursuant to the terms of the relevant Capped Call Transaction. Such termination value will be determined by each Capped Call Counterparty, in its capacity as the calculation agent under its Capped Call Transaction, acting in good faith and in a commercially reasonable manner. The amount of such early termination cash payment would depend on a variety of factors, including the remaining term of its Capped Call Transaction as of the date on which the Merger is consummated, the Per Share Merger Consideration, the volatility of Proofpoint common stock prior to the announcement of the Merger, hedge unwind costs and applicable interest rates.

In addition, following the announcement of the Merger, the Capped Call Counterparties may adjust the terms of the Capped Call Transactions, regardless of whether the Merger is consummated. Each Capped Call Counterparty may determine, in good faith and in a commercially reasonable manner, in its capacity as calculation agent with respect to its Capped Call Transaction, the economic effect of such an announcement on the value of its Capped Call Transaction and may take into account a number of factors, including, the date of the announcement (and the remaining term of its Capped Call Transaction at that time), the stock price of Proofpoint common stock and changes in volatility, stock loan rate, liquidity and expected dividends of Proofpoint common stock, in determining whether an adjustment to its Capped Call Transaction is appropriate. Each Capped Call Counterparty may make additional adjustments to its Capped Call Transaction following the announcement of a change to the Merger, including a withdrawal from, or the abandonment or discontinuation of, the Merger.

The indenture governing the Convertible Notes and the forms of confirmations containing the terms of the Capped Call Transactions were included as exhibits to Proofpoint’s Current Report on Form 8-K filed by Proofpoint with the SEC on August 23, 2019. All references in this section captioned “Capped Call Transactions” to share counts, conversion prices and strike prices may change from time to time in accordance with the terms of the relevant confirmations (the “Capped Call Confirmations”).

Except for a financial outlook with respect to the current fiscal quarter and year issued in connection with its ordinary course earnings announcements, Proofpoint does not, as a matter of course, publicly disclose forecasts or projections as to future performance, earnings or other results due to the inherent unpredictability of the underlying assumptions, estimates and projections, especially over the longer term periods. In connection with the evaluation of the Merger, Proofpoint’s management prepared short-term projections of Proofpoint’s financial results for the second calendar quarter of calendar year 2021, the third and fourth calendar quarters of calendar year 2021, and calendar years 2022 through 2024 (the “Management Plan”). Projections of Proofpoint’s financial results for calendar years 2025 through 2030 were then extrapolated from the foregoing short-term financial projections by Morgan Stanley and approved for use by Morgan Stanley by Proofpoint's management (together with the Management Plan, the “Management Projections”). Proofpoint is including a summary of the Management Projections in order to provide Proofpoint Stockholders with access to information that was made available to, and approved by, the Board of Directors in connection with its evaluation of the Merger and the Per Share Merger Consideration. The Management Plan was also

made available to Parent and Merger Sub at Parent’s request in connection with their due diligence review, and the Management Projections were made available to Morgan Stanley in connection with the rendering of its financial fairness opinion to the Board of Directors as provided in the section of this proxy statement captioned “—Opinion of Morgan Stanley & Co. LLC.”

The following table presents a summary of the Management Projections.

The Management Projections were developed by Proofpoint management on a standalone basis without giving effect to the Merger and the other transactions contemplated by the Merger Agreement. Furthermore, the Management Projections do not take into account the effect of any failure of the transactions contemplated by the Merger Agreement to be completed and should not be viewed as accurate or continuing in that context. Although the Management Projections are presented with numerical specificity, they were based on numerous variables and assumptions made by Proofpoint management with respect to industry performance, general business, economic, regulatory, market and financial conditions and other future events, as well as matters specific to Proofpoint’s business, all of which are difficult or impossible to predict accurately and many of which are beyond Proofpoint’s control. The Management Projections constitute forward-looking information and are subject to many risks and uncertainties that could cause actual results to differ materially from the results forecasted in the Management Projections, including, but not limited to, Proofpoint’s performance, industry performance, general business and economic conditions, customer requirements, staffing levels, competition, adverse changes in applicable laws, regulations or rules, the ability to successfully pursue and complete acquisitions, and the various risks set forth in Proofpoint’s reports filed with the SEC. There can be no assurance that the Management Projections will be realized or that actual results will not be significantly higher or lower than the Management Projections. The Management Projections cover several years, and such information by its nature becomes less reliable with each successive year. In addition, the Management Projections will be affected by Proofpoint’s ability to achieve strategic goals, objectives and targets over the applicable periods. The Management Projections reflect assumptions as to certain business decisions that are subject to change and cannot, therefore, be considered a guarantee of future operating results, and this information should not be relied on as such. The inclusion of the Management Projections should not be regarded as an indication that Proofpoint, Morgan Stanley, their respective officers, directors, affiliates, advisors, or other representatives or anyone who received this information then considered, or now considers, them a reliable prediction of future events, and this information should not be relied upon as such. The inclusion of the Management Projections in this proxy statement should not be regarded as an indication that the Management Projections will be necessarily predictive of actual future events. No representation is made by Proofpoint or any other person regarding the Management Projections or Proofpoint’s ultimate performance compared to such information. The Management Projections should be evaluated, if at all, in conjunction with the historical financial statements and other information about Proofpoint contained in Proofpoint’s public filings with the SEC. For more information, please see the section of this proxy statement captioned “Where You Can Find More Information.” In light of the foregoing factors, and the uncertainties inherent in the Management Projections, Proofpoint Stockholders are cautioned not to place undue, if any, reliance on the Management Projections.

The Management Projections were not prepared with a view toward public disclosure or with a view toward complying with the published guidelines of the SEC regarding projections or accounting principles generally

accepted in the United States (“GAAP”), or the guidelines established by the American Institute of Certified Public Accountants with respect to the preparation or presentation of prospective financial information. The Management Projections included in this proxy statement have been prepared by, and are the responsibility of, the Company’s management. PricewaterhouseCoopers LLP has not audited, reviewed, examined, compiled nor applied agreed-upon procedures with respect to the accompanying Management Projections and, accordingly, PricewaterhouseCoopers LLP does not express an opinion or any other form of assurance with respect thereto. The PricewaterhouseCoopers LLP report incorporated by reference into this proxy statement relates to the Company’s previously issued financial statements. It does not extend to the Management Projections and should not be read to do so.

Revenue, EBIT and Unlevered Free Cash Flow contained in the Management Projections summarized above are “non-GAAP financial measures,” which are financial performance measures that are not calculated in accordance with GAAP. The non-GAAP financial measures used in the Management Projections were relied upon by Morgan Stanley for purposes of its opinion and by the Board of Directors in connection with its evaluation of the Merger. The SEC rules which would otherwise require a reconciliation of a non-GAAP financial measure to a GAAP financial measure do not apply to non-GAAP financial measures included in disclosures relating to a proposed business combination such as the Merger if the disclosure is included in a document such as this proxy statement. In addition, reconciliations of non-GAAP financial measures were not relied upon by Morgan Stanley for purposes of its opinion or by the Board of Directors in connection with its evaluation of the Merger. Accordingly, Proofpoint has not provided a reconciliation of the financial measures included in the Management Projections to the relevant GAAP financial measures. Non-GAAP financial measures should not be considered in isolation from, or as a substitute for, financial information presented in compliance with GAAP, and non-GAAP financial measures as used by Proofpoint may not be comparable to similarly titled amounts used by other companies. Furthermore, there are limitations inherent in non-GAAP financial measures because they exclude charges and credits that are required to be included in a GAAP presentation. Accordingly, these non-GAAP financial measures should be considered together with, and not as an alternative to, financial measures prepared in accordance with GAAP.

The summary of such information above is included solely to give Proofpoint Stockholders access to the information that was made available to the Board of Directors, Morgan Stanley, Parent and Merger Sub, and is not included in this proxy statement in order to influence any Proofpoint Stockholder to make any investment decision with respect to the Merger, including whether or not to seek appraisal rights with respect to their shares of Proofpoint common stock. In addition, the Management Projections have not been updated or revised to reflect information or results after the date they were prepared or as of the date of this proxy statement, and except as required by applicable securities laws, Proofpoint does not intend to update or otherwise revise the Management Projections or the specific portions presented to reflect circumstances existing after the date when made or to reflect the occurrence of future events, even in the event that any or all of the underlying assumptions are shown to be in error.

In considering the recommendation of the Board of Directors that Proofpoint Stockholders vote to adopt the Merger Agreement, Proofpoint Stockholders should be aware that certain of Proofpoint’s non-employee directors and executive officers have interests in the Merger that are different from, or in addition to, those of Proofpoint Stockholders generally. The Board of Directors was aware of and considered these interests, among other matters, in approving the Merger Agreement and the Merger, and in recommending that the Merger Agreement be adopted by Proofpoint Stockholders.

Except as otherwise specifically noted, for purposes of quantifying the potential payments and benefits described in this section, the following assumptions were used:

For purposes of this disclosure, Proofpoint’s named executive officers are: (i) Gary Steele, Chief Executive Officer and the Chairman of our Board of Directors; (ii) Paul Auvil, Chief Financial Officer; (iii) David Knight, Executive Vice President and General Manager, Information and Cloud Security Products Group; (iv) Blake Sallé, Chief Revenue Officer; and (v) Ashan Willy, Executive Vice President and General Manager, Security Products and Services Group. Each of Proofpoint’s current executive officers are its named executive officers.

Although Bhagwat Swaroop, former Executive Vice President, Industry Solutions and Business Development of Proofpoint, is considered an executive officer for purposes of this disclosure, Mr. Swaroop does not hold any Proofpoint equity awards and does not have any interests in the Merger except insofar as he may hold shares of Proofpoint common stock.

As the amounts provided below are estimates based on multiple assumptions that may or may not actually occur or be accurate as of the date referenced, the actual amounts, if any, that may be paid or become payable may materially differ from the amounts set forth below.

At the Effective Time, each Vested Company Option will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Vested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Vested Company Option, subject to any required withholding of taxes.

At the Effective Time, each Unvested Company Option will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Unvested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Unvested Company Option. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company Option Consideration amounts will vest and become payable at the same time as the Company Option from which such Unvested Company Option Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company Option immediately prior to the Effective Time with respect to the receipt of the Unvested Company Option Consideration.

At the Effective Time, each Vested Company RSU (including each Company RSU held by a non-employee director) will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

At the Effective Time, each Unvested Company RSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company RSU Consideration amounts will vest and become payable at

the same time as the Company RSU from which such Unvested Company RSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company RSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company RSU Consideration.

At the Effective Time, each Vested Company PSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Vested Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

At the Effective Time, each Unvested Company PSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company PSU Consideration amounts will vest and be payable at the same time as the Company PSU from which such Unvested Company PSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company PSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company PSU Consideration.

At the Effective Time, each Vested Company RSU (the only equity award held by the non-employee members of the Board of Directors) held by a non-employee member of the Board of Directors will convert into Per Share Merger Consideration in the manner described above. Based on the assumptions described above under the section of this proxy statement captioned “—Interests of Executive Officers and Directors of Proofpoint in the Merger—Certain Assumptions,” the estimated aggregate amounts that would become payable to Proofpoint’s eight (8) non-employee directors in respect of their Vested Company RSUs is $2,389,728, which excludes any grants of Company RSUs that may be made by Proofpoint to the non-employee directors following the date of this proxy statement.

At the Effective Time, each Unvested Company RSU and Unvested Company PSU held by the named executive officers will convert into cash awards of Unvested Company RSU Consideration and Unvested Company PSU Consideration in the manner described above and will generally remain subject to the same time-based vesting conditions and other terms and conditions as were applicable immediately prior to the Effective Time. Each award of Unvested Company RSU Consideration and Unvested Company PSU Consideration will vest in the event that a named executive officer experiences a termination of employment by Proofpoint without cause or by the named executive officer for “good reason,” in either case, within three (3) months prior to the Change in Control Date or, if earlier, upon the date of the Merger Agreement, and following the Change in Control Date, prior to the final vesting date applicable to such awards. At the Effective Time, and as a result of the attainment of the performance metrics applicable to Company PSUs at the target level of performance, a portion of each Company PSU will become a Vested Company PSU and will be paid to the named executive officers shortly following the Effective Time.

See the section of this proxy statement captioned “—Interests of Executive Officers and Directors of Proofpoint in the Merger—Golden Parachute Compensation” for an estimate of the amounts that would become payable to each Proofpoint named executive officer in respect of his Unvested Company RSUs, Unvested Company PSUs and Vested Company PSUs.

Proofpoint has entered into change in control severance agreements with each of its named executive officers (the “Severance Agreements”). The Severance Agreements generally provide that if the named executive officer

is terminated from employment by Proofpoint without cause or the named executive officer terminates his employment with good reason, in either case, within three (3) months prior to the Change in Control Date or, if earlier, upon the date of the Merger Agreement, or within eighteen (18) months following the Change in Control Date, then the named executive officer will receive:

The provision of payments and benefits described above is conditioned upon the named executive officer’s execution of a release of claims. The Severance Agreements further provide that if a named executive officer receives any amount that is subject to the “golden parachute” excise tax imposed pursuant to Section 280G and 4999 of the Code, the amount of the payments to be made to the named executive officer will be reduced to the extent necessary to avoid imposition of the excise tax, but only if the after-tax amount of the reduced payments exceeds the after-tax amount that the executive officer would receive without any such reduction following imposition of the excise tax and all income and related taxes.

Proofpoint may establish a retention program providing for cash retention bonuses in the aggregate amount not to exceed $5.0 million (the “Retention Program”). Awards under the Retention Program will vest and become payable as to (x) 50% on the closing date of the Merger, subject to the grantee’s continued service through such date and (y) 50% on March 31, 2022, or, if earlier, as of the date on or following the closing date of the Merger that the grantee terminates employment due to a termination of employment by Proofpoint without cause or by the grantee for good reason. Awards under the Retention Program may be granted to employees of Proofpoint generally but no award may be granted to Proofpoint’s Chief Executive Officer or Chief Financial Officer. As of the date of this proxy statement, none of the eligible named executive officers has received an award under the Retention Program.

As of the date of this proxy statement, none of the Proofpoint named executive officers has discussed or entered into any agreement with Parent or any of its affiliates regarding employment with, or the right to purchase or participate in the equity of, Parent or one or more of its affiliates. Prior to or following the closing of the Merger, however, some or all of the Proofpoint named executive officers may discuss or enter into agreements with Parent or any of its affiliates regarding employment with, or the right to purchase or participate in the equity of, Parent or one or more of its affiliates.

Pursuant to the terms of the Merger Agreement, Proofpoint’s directors and executive officers will be entitled to certain ongoing indemnification and coverage for a period of six (6) years following the effective time under directors’ and officers’ liability insurance policies from the surviving corporation. This indemnification and insurance coverage is further described in the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Indemnification and Insurance.”

In accordance with Item 402(t) of Regulation S-K under the Securities Act, the table below sets forth the compensation that is based on, or otherwise relates to, the Merger that will or may become payable to each named executive officer of Proofpoint in connection with the Merger. For additional details regarding the terms of the payments and benefits described below, see the section of this proxy statement captioned “—Interests of Executive Officers and Directors of Proofpoint in the Merger.”

The amounts shown in the table below are estimates based on multiple assumptions that may or may not actually occur or be accurate on the relevant date, including the assumptions described below and in the footnotes to the table, and do not reflect certain compensation actions that may occur prior to completion of the Merger, including any equity award grants that may be made after the assumed effective time of May 25, 2021. For

purposes of quantifying the potential payments and benefits described in this section, the following assumptions were used:

Parent and Merger Sub have represented to Proofpoint that they will have available to them, together with Proofpoint's cash on hand, sufficient funds to pay the fees and expenses required to be paid at the closing of the Merger by Parent and Merger Sub under the Merger Agreement. This includes funds needed to: (1) pay Proofpoint Stockholders the amounts due under the Merger Agreement for their Proofpoint common stock, (2) make payments in respect of our outstanding Company Options payable at the closing of the Merger pursuant to the Merger Agreement and (3) make payments of all amounts required to be paid in connection with the Merger pursuant to the Convertible Notes Indenture and the Convertible Notes.

Parent and Merger Sub have obtained committed financing consisting of (i) equity to be provided by the Thoma Bravo Funds pursuant to the terms of the Equity Commitment Letter and (ii) debt financing to be provided pursuant to the Debt Commitment Letter by the lenders party thereto. In connection with the Merger Agreement, Parent and Merger Sub have delivered to Proofpoint copies of the Financing Letters. Notwithstanding anything in the Merger Agreement to the contrary, in no event shall the receipt or availability of any funds or financing (including the financing contemplated by the Financing Letters) by or to Parent or any of its affiliates or any other financing transaction be a condition to any of the obligations of Parent or Merger Sub under the Merger Agreement.

Pursuant to the Equity Commitment Letter, the Thoma Bravo Funds have committed to contribute or cause to be contributed to Parent at the closing of the Merger certain equity financing for the purpose of funding the Required Amounts. The obligations of each Thoma Bravo Fund to provide the equity financing under the Equity Commitment Letter are subject to a number of conditions, including, but not limited to: (i) satisfaction or written waiver by Proofpoint, Parent and Merger Sub, as applicable, of each the conditions to the obligations of Proofpoint, Parent and Merger Sub to consummate the Merger set forth in Section 2.2 of the Merger Agreement (other than those conditions that by their terms are to be satisfied at the closing of the Merger, but subject to the satisfaction or waiver (to the extent permitted hereunder) of such conditions), (ii) the substantially concurrent consummation of the Merger in accordance with the terms of the Merger Agreement and (iii) the receipt of the debt financing contemplated by the Debt Commitment Letter or, if applicable, alternative debt financing or written confirmation that the debt financing contemplated by the Debt Commitment Letter or, if applicable, alternative debt financing, will be funded at the closing of the Merger if the equity financing under the Equity Commitment Letter is consummated at the closing of the Merger. We refer to the equity financing described in the preceding sentence as the “Equity Financing.”

The obligation of the Thoma Bravo Funds to fund the equity commitment will automatically and immediately terminate upon the earliest to occur of: (i) the consummation of the closing of the Merger and the payment of the aggregate Per Share Merger Consideration and the payment or provision for the other Required Amounts in accordance with the Merger Agreement, (ii) the termination of the Merger Agreement in accordance with its terms, (iii) ninety (90) days after the End Date and (iv) the date that Proofpoint or any of its subsidiaries or any of their respective directors or officers acting on their behalf attempt to enforce the Equity Commitment Letter (except as permitted thereunder).

Proofpoint is an express third-party beneficiary of the Equity Commitment Letter solely with respect to enforcing Parent’s right to cause the commitment under the Equity Commitment Letter by a Thoma Bravo Fund to be funded to Parent in accordance with the Equity Commitment Letter, and to cause Parent to enforce its rights against such Thoma Bravo Fund to perform its funding obligations under the Equity Commitment Letter, in each case subject to (i) the limitations and conditions set forth in the Equity Commitment Letter and (ii) the terms and conditions of the Merger Agreement.

The Debt Commitment Letter provides that the lenders party thereto will provide, upon the terms and subject to the conditions set forth in the Debt Commitment Letter, debt financing (the “Debt Financing”).

The proceeds of the Debt Financing will be used (i) to effect the Merger and related transactions on the Closing Date, (ii) for working capital, capital expenditures and other general corporate purposes and (iii) to pay fees and expenses related to the Merger and related transactions.

The obligations of the lenders party to the Debt Commitment Letter to provide the Debt Financing under the Debt Commitment Letter are subject to a number of customary conditions, including, but not limited to (as applicable):

As of the date hereof, the documentation governing the Debt Financing contemplated by the Debt Commitment Letter has not been finalized and, accordingly, the actual terms of the Debt Financing may differ from those described in this proxy statement.

Pursuant to the Guaranty, the Thoma Bravo Funds have agreed to guarantee the due, punctual and complete payment and performance of: (1) the aggregate amount of the Parent Termination Fee (as defined in the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Termination Fee.”) solely if and when any of the Parent Termination Fee is payable pursuant to the Merger Agreement; (2) any enforcement expenses due by Parent pursuant to legal proceedings as a result of certain defaults under the Merger Agreement; (3) the reimbursement obligations of Parent pursuant to the indemnification obligations to Proofpoint and its representatives in connection with debt financing; and (4) any and all damages, losses, costs and expenses resulting from Parent or Merger Sub’s willful and material breach of the Merger Agreement, subject to certain limitations. We refer to the obligations set forth in the preceding sentence as the “Guaranteed Obligations.” The obligations of the Thoma Bravo Funds under the Guaranty are subject to an aggregate cap equal to $686.4 million.

Subject to specified exceptions, the Guaranty will terminate upon the earliest of:

The closing of the Merger will take place at 5:00 a.m., Pacific time, on the second (2^nd) business day following the satisfaction or waiver of all conditions to closing of the Merger (as described in the section of this proxy statement captioned, “Proposal 1: Adoption of the Merger Agreement—Conditions to the Closing of the Merger”), other than conditions that by their terms are to be satisfied at the closing but subject to the satisfaction or waiver of such conditions.

If the Merger is consummated, Proofpoint Stockholders who continuously hold shares of Proofpoint common stock through the Effective Time, who do not vote in favor of the adoption of the Merger Agreement and who properly demand appraisal of their shares and who do not withdraw their demands or otherwise lose their rights of appraisal will be entitled to seek appraisal of their shares in connection with the Merger under Section 262 the DGCL (“Section 262”). The following discussion is not a complete statement of the law pertaining to appraisal rights under the DGCL and is qualified in its entirety by the full text of Section 262, which is attached to this proxy statement as Annex D and incorporated herein by reference. The following summary does not constitute any legal or other advice and does not constitute a recommendation that Proofpoint Stockholders exercise their appraisal rights under Section 262. All references in Section 262 and in this summary to a “stockholder” are to the record holder of shares of Proofpoint common stock unless otherwise expressly noted herein. Only a holder of record of shares of Proofpoint common stock is entitled to demand appraisal of the shares registered in that holder’s name. A person having a beneficial interest in shares of Proofpoint common stock held of record in the name of another person, such as a bank, broker, trust or other nominee, must act promptly to cause the record holder to follow the steps summarized below properly and in a timely manner to perfect appraisal rights. If you hold your shares of Proofpoint common stock through a bank, broker or other nominee and you wish to exercise appraisal rights, you should consult with your bank, broker or the other nominee.

Under Section 262, if the Merger is completed, Proofpoint Stockholders who: (i) submit a written demand for appraisal of their shares; (ii) do not vote in favor of the adoption of the Merger Agreement; (iii) continuously are the record holders of such shares through the Effective Time; and (iv) otherwise exactly follow the procedures set forth in Section 262, may be entitled to have their shares appraised by the Delaware Court of Chancery and to receive payment in cash of the “fair value” of the shares of Proofpoint common stock, exclusive of any element of value arising from the accomplishment or expectation of the Merger, together with interest to be paid on the amount determined to be “fair value,” if any, as determined by the court. However, after an appraisal petition has been filed, the Delaware Court of Chancery will dismiss appraisal proceedings as to all Proofpoint Stockholders who have asserted appraisal rights unless (a) the total number of shares for which appraisal rights have been pursued and perfected exceeds 1% of the outstanding shares of Proofpoint common stock as measured in accordance with subsection (g) of Section 262; or (b) the value of the aggregate Per Share Merger Consideration in respect of the shares of Proofpoint common stock for which appraisal rights have been pursued and perfected exceeds $1 million (conditions (a) and (b) referred to as the “ownership thresholds”). Unless the Delaware Court of Chancery, in its discretion, determines otherwise for good cause shown, interest on an appraisal award will compound quarterly and accrue at 5% over the Federal Reserve System (the “Federal Reserve”) discount rate (including any surcharge) as established from time to time during the period from the Effective Time through the date the judgment is paid. However, at any time before the Delaware Court of Chancery enters judgment in the appraisal proceedings, the Surviving Corporation may voluntarily pay to each stockholder entitled to appraisal an amount in cash pursuant to subsection (h) of Section 262, in which case such interest will accrue after the time of such payment only on an amount that equals the difference, if any, between the amount so paid and the “fair value” of the shares as determined by the Delaware Court of Chancery, in

addition to any interest accrued prior to the time of such voluntary cash payment, unless paid at such time. The Surviving Corporation is under no obligation to make such voluntary cash payment prior to such entry of judgment.

Under Section 262, where a merger agreement is to be submitted for adoption at a meeting of stockholders, the corporation, not less than twenty (20) days prior to the meeting, must notify each of its stockholders who was such on the record date for notice of such meeting with respect to shares for which appraisal rights are available that appraisal rights are available and include in the notice a copy of Section 262. This proxy statement constitutes Proofpoint’s notice to Proofpoint Stockholders that appraisal rights are available in connection with the Merger, and the full text of Section 262 is attached to this proxy statement as Annex D. In connection with the Merger, any Proofpoint Stockholder who wishes to exercise appraisal rights, or who wishes to preserve his, her or its right to do so, should review Annex D carefully. Failure to strictly comply with the requirements of Section 262 in a timely and proper manner may result in the loss of appraisal rights under the DGCL. A Proofpoint Stockholder who loses his, her or its appraisal rights will be entitled to receive the Per Share Merger Consideration described in the Merger Agreement. Moreover, because of the complexity of the procedures for exercising the right to seek appraisal of shares of Proofpoint common stock, Proofpoint believes that if a Proofpoint Stockholder considers exercising such rights, that Proofpoint Stockholder should seek the advice of legal counsel.

Proofpoint Stockholders wishing to exercise the right to seek an appraisal of their shares of Proofpoint common stock must do ALL of the following:

In addition, one of the ownership thresholds must be met.

Because a proxy that does not contain voting instructions will, unless revoked, be voted in favor of the adoption of the Merger Agreement, a Proofpoint Stockholder who votes by proxy and who wishes to exercise appraisal rights must vote against the adoption of the Merger Agreement, abstain or not vote his, her or its shares.

Any Proofpoint Stockholder wishing to exercise appraisal rights must deliver to Proofpoint, before the vote on the adoption of the Merger Agreement at the Special Meeting at which the proposal to adopt the Merger Agreement will be submitted to Proofpoint Stockholders, a written demand for the appraisal of the Proofpoint Stockholder’s shares, and that Proofpoint Stockholder must not vote or submit a proxy in favor of the adoption of the Merger Agreement. A holder of shares of Proofpoint common stock exercising appraisal rights must hold of record the shares on the date the written demand for appraisal is made and must continue to hold the shares of record through the Effective Time. A proxy that is submitted and does not contain voting instructions will, unless revoked, be voted in favor of the adoption of the Merger Agreement, and it will constitute a waiver of the Proofpoint Stockholder’s right of appraisal and will nullify any previously delivered written demand for appraisal. Therefore, a Proofpoint Stockholder who submits a proxy and who wishes to exercise appraisal rights must ensure that the proxy submitted contains instructions to vote against the adoption of the Merger Agreement or abstain from voting. Neither voting against the adoption of the Merger Agreement nor abstaining from voting on the proposal to adopt the Merger Agreement will, in and of itself, constitute a written demand for appraisal satisfying the requirements of Section 262. The written demand for appraisal must be in addition to and separate from any proxy or vote on the adoption of the Merger Agreement. A Proofpoint Stockholder’s failure to make

the written demand prior to the taking of the vote on the adoption of the Merger Agreement at the Special Meeting of Proofpoint Stockholders will constitute a waiver of appraisal rights.

Only a Proofpoint Stockholder of record is entitled to demand appraisal rights for the shares registered in that holder’s name. A demand for appraisal in respect of shares of Proofpoint common stock must be executed by or on behalf of the holder of record, and must reasonably inform Proofpoint of the identity of the holder and state that the person intends thereby to demand appraisal of the holder’s shares in connection with the Merger. If the shares are owned of record in a fiduciary or representative capacity, such as by a trustee, guardian or custodian, such demand must be executed by or on behalf of the record owner, and if the shares are owned of record by more than one (1) person, as in a joint tenancy and tenancy in common, the demand must be executed by or on behalf of all joint owners. An authorized agent, including an authorized agent for two (2) or more joint owners, may execute a demand for appraisal on behalf of a holder of record; however, the agent must identify the record owner or owners and expressly disclose that, in executing the demand, the agent is acting as agent for the record owner or owners.

PROOFPOINT STOCKHOLDERS WHO HOLD THEIR SHARES IN BROKERAGE OR BANK ACCOUNTS OR OTHER NOMINEE FORMS AND WHO WISH TO EXERCISE APPRAISAL RIGHTS SHOULD CONSULT WITH THEIR BANK, BROKER OR OTHER NOMINEES, AS APPLICABLE, TO DETERMINE THE APPROPRIATE PROCEDURES FOR THE BANK, BROKER OR OTHER NOMINEE TO MAKE A DEMAND FOR APPRAISAL OF THOSE SHARES. A PERSON HAVING A BENEFICIAL INTEREST IN SHARES HELD OF RECORD IN THE NAME OF ANOTHER PERSON, SUCH AS A BANK, BROKER OR OTHER NOMINEE, MUST ACT PROMPTLY TO CAUSE THE RECORD HOLDER TO FOLLOW PROPERLY AND IN A TIMELY MANNER THE STEPS NECESSARY TO PERFECT APPRAISAL RIGHTS.

All written demands for appraisal pursuant to Section 262 should be mailed or delivered to:

Proofpoint, Inc.

Attention: General Counsel

925 West Maude Avenue

Sunnyvale, California 94085

Any Proofpoint Stockholder who has delivered a written demand to Proofpoint and who has not commenced an appraisal proceeding or joined that proceeding as a named party may withdraw his, her or its demand for appraisal and accept the Per Share Merger Consideration offered pursuant to the Merger Agreement by delivering to Proofpoint a written withdrawal of the demand for appraisal. However, any such attempt to withdraw the demand made more than sixty (60) days after the Effective Time will require written approval of the Surviving Corporation. No appraisal proceeding in the Delaware Court of Chancery will be dismissed as to any Proofpoint Stockholder without the approval of the Delaware Court of Chancery, and such approval may be conditioned upon such terms as the Delaware Court of Chancery deems just; provided, however, that this shall not affect the right of any Proofpoint Stockholder who has not commenced an appraisal proceeding or joined that proceeding as a named party to withdraw such Proofpoint Stockholder’s demand for appraisal and to accept the Per Share Merger Consideration within sixty (60) days after the Effective Time. If an appraisal proceeding is commenced and Proofpoint, as the Surviving Corporation, does not approve a request to withdraw a demand for appraisal when that approval is required, or, except with respect to any Proofpoint Stockholder who withdraws such Proofpoint Stockholder’s demand in accordance with the proviso in the immediately preceding sentence, if the Delaware Court of Chancery does not approve the dismissal of an appraisal proceeding with respect to a Proofpoint Stockholder, the Proofpoint Stockholder will be entitled to receive only the appraised value determined in any such appraisal proceeding, which value could be less than, equal to or more than the Per Share Merger Consideration being offered pursuant to the Merger Agreement.

If the Merger is completed, within ten (10) days after the Effective Time, the Surviving Corporation will notify each holder of shares of Proofpoint common stock who has properly made a written demand for appraisal pursuant to Section 262, and who has not voted in favor of the adoption of the Merger Agreement, that the Merger has become effective and the effective date thereof.

Within one hundred twenty (120) days after the Effective Time, but not thereafter, the Surviving Corporation or any Proofpoint Stockholder who has complied with Section 262 and is entitled to seek appraisal under Section 262 (including for this purpose any beneficial owner of the relevant shares) may commence an appraisal proceeding by filing a petition in the Delaware Court of Chancery, with a copy served on the Surviving Corporation in the case of a petition filed by a Proofpoint Stockholder (or beneficial owner), demanding a determination of the “fair value” of the shares held by all dissenting Proofpoint Stockholders entitled to appraisal. The Surviving Corporation is under no obligation, and has no present intention, to file a petition, and Proofpoint Stockholders should not assume that the Surviving Corporation will file a petition or initiate any negotiations with respect to the “fair value” of the shares of Proofpoint common stock. Accordingly, any Proofpoint Stockholder who desire to have their shares appraised should initiate all necessary action to perfect their appraisal rights in respect of their shares of Proofpoint common stock within the time and in the manner prescribed in Section 262. The failure of a holder of Proofpoint common stock to file such a petition within the period specified in Section 262 could nullify the Proofpoint Stockholder’s previous written demand for appraisal.

Within one hundred twenty (120) days after the Effective Time, any holder of shares of Proofpoint common stock who has complied with the requirements of Section 262 and who is entitled to appraisal rights thereunder will be entitled, upon written request, to receive from the Surviving Corporation a statement setting forth the aggregate number of shares not voted in favor of the adoption of the Merger Agreement and with respect to which Proofpoint has received demands for appraisal, and the aggregate number of holders of such shares. The Surviving Corporation must mail this statement to the requesting Proofpoint Stockholder within ten (10) days after receipt by the Surviving Corporation of the written request for such a statement or within ten (10) days after the expiration of the period for delivery of demands for appraisal, whichever is later. A beneficial owner of shares of Proofpoint common stock held either in a voting trust or by a nominee on behalf of such person may, in such person’s own name, file a petition seeking appraisal or request from the Surviving Corporation the foregoing statements. As noted above, however, the demand for appraisal can only be made by a Proofpoint Stockholder of record.

If a petition for an appraisal is duly filed by a holder of shares of Proofpoint common stock and a copy thereof is served upon the Surviving Corporation, the Surviving Corporation will then be obligated within twenty (20) days after such service to file with the Delaware Register in Chancery a duly verified list containing the names and addresses of all Proofpoint Stockholders who have demanded payment for their shares and with whom agreements as to the value of their shares have not been reached. Upon the filing of any such petition, the Delaware Court of Chancery may order that notice of the time and place fixed for the hearing on the petition be mailed to the Surviving Corporation and all of Proofpoint Stockholders shown on the written statement described above at the addresses stated therein. Such notice will also be published at least one (1) week before the day of the hearing in a newspaper of general circulation published in the City of Wilmington, Delaware, or in another publication determined by the court. The costs of these notices are borne by the Surviving Corporation. After notice to Proofpoint Stockholders as required by the court, the Delaware Court of Chancery is empowered to conduct a hearing on the petition to determine those Proofpoint Stockholders who have complied with Section 262 and who have become entitled to appraisal rights thereunder. The Delaware Court of Chancery may require Proofpoint Stockholders who demanded payment for their shares to submit their stock certificates (if any) to the Delaware Register in Chancery for notation thereon of the pendency of the appraisal proceedings and, if any Proofpoint Stockholder fails to comply with the direction, the Delaware Court of Chancery may dismiss that Proofpoint Stockholder from the proceedings. The Delaware Court of Chancery will dismiss appraisal proceedings as to all Proofpoint Stockholders who have asserted appraisal rights if neither of the ownership thresholds is met.

After determining Proofpoint Stockholders entitled to appraisal and that at least one of the ownership thresholds described above has been satisfied as to Proofpoint Stockholders seeking appraisal rights, the appraisal proceeding will be conducted in accordance with the rules of the Delaware Court of Chancery, including any rules specifically governing appraisal proceedings. Through such proceeding, the Delaware Court of Chancery will determine the “fair value” of the shares of Proofpoint common stock, exclusive of any element of value arising from the accomplishment or expectation of the Merger, together with interest, if any, to be paid upon the amount determined to be the “fair value.” In determining “fair value,” the Delaware Court of Chancery will

take into account all relevant factors. Unless the court in its discretion determines otherwise for good cause shown, interest from the Effective Time through the date of payment of the judgment will compound quarterly and accrue at 5% over the Federal Reserve discount rate (including any surcharge) as established from time to time during the period from the Effective Time through the date the judgment is paid. However, at any time before the Delaware Court of Chancery enters judgment in the appraisal proceedings, the Surviving Corporation may pay to each Proofpoint Stockholder entitled to appraisal an amount in cash, in which case such interest will accrue after the time of such payment only on an amount that equals the difference, if any, between the amount so paid and the “fair value” of the shares as determined by the Delaware Court of Chancery, in addition to any interest accrued prior to the time of such voluntary payment, unless paid at such time.

In Weinberger v. UOP, Inc., the Supreme Court of Delaware discussed the factors that could be considered in determining “fair value” in an appraisal proceeding, stating that “proof of value by any techniques or methods which are generally considered acceptable in the financial community and otherwise admissible in court” should be considered, and that “[f]air price obviously requires consideration of all relevant factors involving the value of a company.” The Supreme Court of Delaware stated that, in making this determination of “fair value,” the court must consider market value, asset value, dividends, earnings prospects, the nature of the enterprise and any other facts that could be ascertained as of the date of the Merger that throw any light on future prospects of the merged corporation. Section 262 provides that “fair value” is to be “exclusive of any element of value arising from the accomplishment or expectation of the Merger.” In Cede & Co. v. Technicolor, Inc., the Supreme Court of Delaware stated that such exclusion is a “narrow exclusion [that] does not encompass known elements of value,” but which rather applies only to the speculative elements of value arising from such accomplishment or expectation. In Weinberger, the Supreme Court of Delaware also stated that “elements of future value, including the nature of the enterprise, which are known or susceptible of proof as of the date of the Merger and not the product of speculation, may be considered.” In addition, the Delaware courts have decided that the statutory appraisal remedy, depending on factual circumstances, may or may not be a dissenting Proofpoint Stockholder’s exclusive remedy.

Proofpoint Stockholders considering seeking appraisal should be aware that the “fair value” of their shares as so determined by the Delaware Court of Chancery could be more than, the same as or less than the Per Share Merger Consideration they would receive pursuant to the Merger if they did not seek appraisal of their shares and that an opinion of an investment banking firm as to the fairness from a financial point of view of the Per Share Merger Consideration payable in a Merger is not an opinion as to, and does not in any manner address, “fair value” under Section 262. No representation is made as to the outcome of the appraisal of “fair value” as determined by the Delaware Court of Chancery, and Proofpoint Stockholders should recognize that such an appraisal could result in a determination of a value higher or lower than, or the same as, the Per Share Merger Consideration. Neither Proofpoint nor Parent anticipates offering more than the Per Share Merger Consideration to any Proofpoint Stockholder exercising appraisal rights, and each of Proofpoint and Parent reserves the rights to make a voluntary cash payment pursuant to subsection (h) of Section 262 and to assert, in any appraisal proceeding, that for purposes of Section 262, the “fair value” of a share of Proofpoint common stock is less than the Per Share Merger Consideration. If a petition for appraisal is not timely filed, or if neither of the ownership thresholds described above has been satisfied as to Proofpoint Stockholders seeking appraisal rights, then the right to an appraisal will cease. The costs of the appraisal proceedings (which do not include attorneys’ fees or the fees and expenses of experts) may be determined by the Delaware Court of Chancery and charged upon the parties as the Delaware Court of Chancery deems equitable under the circumstances. Upon application of a Proofpoint Stockholder, the Delaware Court of Chancery may also order that all or a portion of the expenses incurred by a Proofpoint Stockholder in connection with an appraisal proceeding, including, without limitation, reasonable attorneys’ fees and the fees and expenses of experts, be charged pro rata against the value of all the shares entitled to be appraised. In the absence of such determination or assessment, each party bears its own expenses.

If any Proofpoint Stockholder who demands appraisal of his, her or its shares of Proofpoint common stock under Section 262 fails to perfect, or effectively loses or withdraws, such holder’s right to appraisal, the stockholder’s shares of Proofpoint common stock will be deemed to have been converted at the Effective Time into the right to receive the Per Share Merger Consideration. A Proofpoint Stockholder will fail to perfect, or effectively lose or withdraw, the holder’s right to appraisal if no petition for appraisal is filed within one hundred twenty (120) days

after the Effective Time, if neither of the ownership thresholds described above has been satisfied as to Proofpoint Stockholders seeking appraisal rights or if the Proofpoint Stockholder delivers to the Surviving Corporation a written withdrawal of the holder’s demand for appraisal and an acceptance of the Per Share Merger Consideration in accordance with Section 262.

From and after the Effective Time, no Proofpoint Stockholder who has demanded appraisal rights will be entitled to vote such shares of Proofpoint common stock for any purpose or to receive payment of dividends or other distributions on the stock, except dividends or other distributions on the holder’s shares of Proofpoint common stock, if any, payable to Proofpoint Stockholders as of a time prior to the Effective Time. If no petition for an appraisal is filed, if neither of the ownership thresholds described above has been satisfied as to Proofpoint Stockholders seeking appraisal rights, or if the Proofpoint Stockholder delivers to the Surviving Corporation a written withdrawal of the demand for an appraisal and an acceptance of the Merger, either within sixty (60) days after the Effective Time or thereafter with the written approval of the Surviving Corporation, then the right of such Proofpoint Stockholder to an appraisal will cease. Once a petition for appraisal is filed with the Delaware Court of Chancery, however, the appraisal proceeding may not be dismissed as to any Proofpoint Stockholder without the approval of the court, and such approval may be conditioned upon such terms as the court deems just; provided, however, that the foregoing shall not affect the right of any Proofpoint Stockholder who has not commenced an appraisal proceeding or joined that proceeding as a named party to withdraw such Proofpoint Stockholder’s demand for appraisal and to accept the terms offered upon the Merger within sixty (60) days after the Effective Time.

Failure to comply strictly with all of the procedures set forth in Section 262 may result in the loss of a Proofpoint Stockholder’s statutory appraisal rights. Consequently, any Proofpoint Stockholder wishing to exercise appraisal rights is encouraged to consult legal counsel before attempting to exercise those rights.

Between June 3 and June 11, 2021, four complaints have been filed in the United States District Court for the Southern District of New York against Proofpoint and its directors: Stein v. Proofpoint, Inc., et al., Case No. 1:21-cv-04925 (S.D.N.Y.) (filed June 3, 2021); Ciccotelli v. Proofpoint, Inc., et al., Case No. 1:21-cv-05179 (S.D.N.Y.) (filed June 10, 2021); Ho v. Proofpoint, Inc., et al., Case No. 1:21-cv-05203 (S.D.N.Y.) (filed June 11, 2021); and Theodore v. Proofpoint, Inc., et al., Case No. 1:21-cv-05232 (S.D.N.Y.) (filed June 11, 2021). The complaints each allege that the preliminary proxy statement issued in connection with the proposed merger between Proofpoint and Thoma Bravo omitted material information which rendered the preliminary proxy statement false and misleading. Specifically, the complaints allege that the preliminary proxy statement failed to disclose material information regarding Proofpoint’s financial projections and Morgan Stanley’s financial analyses (the Ciccotelli complaint also alleged that the preliminary proxy statement failed to disclose past services provided by Morgan Stanley to Thoma Bravo and its affiliates).

Each complaint seeks an order enjoining the proposed merger unless and until additional disclosures are issued; rescinding the proposed merger if it closes; awarding damages; awarding costs, including attorneys’ fees, expert fees and expenses; and awarding such other relief as the court deems proper. The defendants believe the complaints are without merit. It is possible additional lawsuits may be filed between the date of this proxy statement and consummation of the Merger.

The Merger will be accounted for as a “purchase transaction” for financial accounting purposes.

The following discussion is a summary of certain U.S. federal income tax consequences of the Merger that may be relevant to Proofpoint Stockholders whose shares are converted into the right to receive cash pursuant to the Merger. This discussion is based upon the Code, Treasury Regulations promulgated under the Code, rulings and other published positions of the Internal Revenue Service (the “IRS”) and judicial decisions, all as in effect on the date of this proxy statement and all of which are subject to change or differing interpretations, possibly with retroactive effect. This discussion is limited to holders who hold their shares of Proofpoint common stock as “capital assets” within the meaning of Section 1221 of the Code (generally, property held for investment purposes). For purposes of this discussion, a “holder” means either a U.S. Holder (as defined below) or a Non-U.S. Holder (as defined below) or both, as the context may require.

This discussion is for general information purposes only and does not address all of the tax consequences that may be relevant to holders in light of their particular facts and circumstances, nor does it address any consequences to holders subject to special rules under the U.S. federal income tax laws, such as:

This discussion does not address any U.S. federal tax consequences other than those pertaining to the income tax (such as estate, gift or other non-income tax consequences) or any state, local or non-U.S. income or non-income tax consequences, or the consequences of the Medicare tax on net investment income. If a partnership (including an entity or arrangement treated as a partnership for U.S. federal income tax purposes) is a beneficial owner of shares of Proofpoint common stock, the U.S. federal income tax treatment of a partner in such partnership will generally depend upon the status of the partner and the activities of the partnership. Partnerships holding shares of Proofpoint common stock and partners therein should consult their own tax advisors regarding the consequences of the Merger to their particular circumstances.

No ruling has been or will be sought from the IRS regarding the U.S. federal income tax consequences of the Merger described herein. This summary is not binding on the IRS or a court, and there can be no assurance that the tax consequences described in this summary will not be challenged by the IRS or that they would be sustained by a court if so challenged.

THIS DISCUSSION IS PROVIDED FOR GENERAL INFORMATION ONLY. HOLDERS SHOULD CONSULT THEIR OWN TAX ADVISORS CONCERNING THE U.S. FEDERAL INCOME TAX CONSEQUENCES RELATING TO THE MERGER IN LIGHT OF THEIR PARTICULAR CIRCUMSTANCES AND ANY CONSEQUENCES ARISING UNDER ANY STATE, LOCAL, NON-U.S. OR OTHER TAX LAWS.

This section applies to “U.S. Holders.” For purposes of this discussion, a “U.S. Holder” means a beneficial owner of shares of Proofpoint common stock that is, for U.S. federal income tax purposes:

The receipt of cash by a U.S. Holder in exchange for shares of Proofpoint common stock pursuant to the Merger will be a taxable transaction for U.S. federal income tax purposes. In general, a U.S. Holder will recognize gain or loss in an amount equal to the difference, if any, between the amount of cash received and the U.S. Holder’s adjusted tax basis in the shares of Proofpoint common stock surrendered pursuant to the Merger. A U.S. Holder’s adjusted tax basis generally will equal the amount that such U.S. Holder paid for the shares of Proofpoint common stock. Such gain or loss will be capital gain or loss and will be long-term capital gain or loss if such U.S. Holder’s holding period in such shares is more than one year at the time of the Merger. A reduced tax rate on capital gain will generally apply to long-term capital gain of a non-corporate U.S. Holder. The deductibility of capital losses is subject to limitations.

This section applies to “Non-U.S. Holders.” For purposes of this discussion, a “Non-U.S. Holder” means a beneficial owner of shares of Proofpoint common stock that is neither a U.S. Holder nor a partnership for U.S. federal income tax purposes.

Special rules not discussed below may apply to certain Non-U.S. Holders subject to special tax treatment, such as “controlled foreign corporations” or “passive foreign investment companies.” Non-U.S. Holders should consult their tax advisors to determine the U.S. federal, state, local and non-U.S. tax consequences that may be relevant to them in light of their particular circumstances.

Any gain realized by a Non-U.S. Holder pursuant to the Merger will generally not be subject to U.S. federal income tax unless:

Information reporting and backup withholding (currently, at a rate of 24%) may apply to the proceeds received by a holder pursuant to the Merger. Backup withholding generally will not apply to (i) a U.S. Holder that furnishes a correct taxpayer identification number and certifies that such U.S. Holder is not subject to backup withholding on IRS Form W-9 (or a substitute successor form) or (ii) a Non-U.S. Holder that provides a certification of such Non-U.S. Holder’s foreign status on the appropriate series of IRS Form W-8 (or a substitute or successor form) or otherwise establishes an exemption from backup withholding. Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules will be allowed as a refund or a credit against the holder’s U.S. federal income tax liability; provided that the required information is timely furnished to the IRS.

HOLDERS OF PROOFPOINT COMMON STOCK SHOULD CONSULT THEIR OWN TAX ADVISORS REGARDING THE TAX CONSEQUENCES OF THE MERGER TO THEIR PARTICULAR CIRCUMSTANCES, INCLUDING THE APPLICABILITY OF ANY STATE, LOCAL, NON-U.S. OR OTHER TAX LAWS.

Proofpoint and Parent have agreed to take all action necessary to comply with all regulatory notification requirements, and, subject to certain limitations, to obtain all regulatory approvals required to consummate the Merger and the other transactions contemplated by the Merger Agreement. These approvals include approval under the HSR Act and any other applicable antitrust laws (whether domestic or foreign).

Under the HSR Act and the rules promulgated thereunder, the Merger may not be completed until Proofpoint and Thoma Bravo each files a Notification and Report Form with the Antitrust Division of the U.S. Department of Justice (“DOJ”) and the Federal Trade Commission (“FTC”), and the applicable waiting period has expired or been terminated. A transaction notifiable under the HSR Act may not be completed until the expiration of a 30-calendar-day waiting period following the parties’ filings of their respective HSR Act notification and report forms. If the FTC or DOJ issues a request for additional information and documents (which we refer to as a “Second Request”) prior to the expiration of the initial waiting period, the parties must observe a second 30-day waiting period, which would begin to run only after both parties have substantially complied with the Second Request.

Proofpoint and the Thoma Bravo Funds each filed a Notification and Report Form under the HSR Act with respect to the Merger with the FTC and DOJ on May 14, 2021. The HSR waiting period is expected to expire at 11:59 p.m., Eastern time on June 14, 2021.

At any time before or after consummation of the Merger, notwithstanding the termination or expiration of the waiting period under the HSR Act, the FTC, the DOJ or any state could take such action under the antitrust laws as it deems necessary or desirable in the public interest, including seeking to enjoin the completion of the Merger, seeking divestiture of substantial assets of the parties, or seeking to require the parties to license or hold separate assets or terminate existing relationships and contractual rights. Private parties may also seek to take legal action under the antitrust laws under certain circumstances. We cannot be certain that a challenge to the Merger will not be made or that, if a challenge is made, we will prevail.

The Merger is also subject to clearance or approval by the relevant antitrust authorities in Germany and Austria.

Under the German Act Against Restraints of Competition (“ARC”), the Merger cannot be consummated unless the parties have filed a notification with the German Federal Cartel Office (“FCO”) and the Merger has been cleared or the applicable waiting period has expired. The initial waiting period is one month. This period may be shortened if the FCO informs the notifying parties that it has no concerns with regard to the transaction. If the FCO believes that the transaction would violate the ARC by significantly impeding effective competition in any of the product markets affected by the transaction in Germany, it may initiate second phase proceedings that would result either in a prohibition or clearance of the Merger within four months from commencement of the second phase proceedings. The second phase four-(4)-month period is suspended if the FCO has to again request information from a party involved in the Merger, because the party has failed, for reasons for which the undertaking is responsible, to comply with a prior request for information in full or in a timely manner. The suspension ends as soon as the party has submitted all the information requested to the FCO. The four-(4)-month period is extended by one month if, for the first time during the proceedings, a notifying party proposes to the FCO conditions and obligations to remove competitive concerns. Further, the notifying parties can consent to an extension of the second phase four-(4)-month period.

Under the Austrian Cartel Act, the Merger cannot be consummated unless the parties have filed a notification with the Federal Competition Authority (“FCA”), and the Merger has been cleared or the applicable waiting period has expired. The initial waiting period is four weeks. Within the initial waiting period, either the FCA or the Cartel Court may initiate second phase proceedings for an in-depth review of the Merger before the Cartel Court that would result either in a prohibition or clearance of the Merger within five (5) months from commencement of the second phase proceedings. This period can be extended by one (1) month upon request by the notifying party.

The Merger is subject to the expiration of the applicable review periods under, or the receipt of approvals or clearances under, the relevant foreign investment laws of Australia, France and, subject to full commencement of the relevant laws, the United Kingdom, in each case unless a relevant exemption applies. In addition, relevant regulatory bodies could take action under other applicable regulatory laws as they deem necessary or desirable in the public interest, including, without limitation, seeking to enjoin or otherwise prevent the completion of the Merger or permitting completion subject to regulatory conditions. Private parties may also seek to take legal action under regulatory laws under some circumstances. There can be no assurance that a challenge to the Merger on regulatory grounds will not be made or, if such a challenge is made, that it would not be successful.

under the caption, “—Conditions to the Closing of the Merger”) (other than those conditions to be satisfied at the closing of the Merger) or such other time agreed to in writing by Parent, Proofpoint and Merger Sub. However, if a specified marketing period (being the first period of fifteen (15) consecutive business days following the date on which Parent has been provided the required financial information regarding Proofpoint required by the Debt Commitment Letter), has not ended at the time of the satisfaction or waiver of all conditions to closing of the Merger (other than those conditions to be satisfied at the closing of the Merger), the closing of the Merger will then occur on the date that is the earlier of (i) any business day during such marketing period specified by Parent to Proofpoint on no less than two (2) business days’ notice to Proofpoint and (ii) the second (2^nd) business day after the final day of such marketing period.

On the Closing Date, the parties will file a certificate of merger with the Secretary of State for the State of Delaware as provided under the DGCL. The time at which the Merger will become effective will occur at the Effective Time.

At the Effective Time, and without any action required by any Proofpoint Stockholder, each share of Proofpoint common stock (other than Excluded Shares, which include, for example, shares of Proofpoint common stock owned by Proofpoint Stockholders who have properly and validly exercised their statutory rights of appraisal under Section 262 of the DGCL) outstanding as of immediately prior to the Effective Time will be cancelled and extinguished, and automatically converted into the right to receive the Per Share Merger Consideration, less any applicable withholding taxes.

The Merger Agreement provides that Proofpoint’s equity awards that are outstanding immediately prior to the Effective Time will be subject to the following treatment as of the Effective Time:

Each Vested Company Option will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Vested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Vested Company Option, subject to any required withholding of taxes.

Each Unvested Company Option will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the excess, if any, of (i) the Per Share Merger Consideration over (ii) the per share exercise price for such Unvested Company Option, by (y) the total number of shares of Proofpoint common stock underlying such Unvested Company Option. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company Option Consideration amounts will vest and become payable at the same time as the Company Option from which such Unvested Company Option Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company Option immediately prior to the Effective Time with respect to the receipt of the Unvested Company Option Consideration.

Each Vested Company RSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company RSU, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company RSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company

RSU, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company RSU Consideration amounts will vest and become payable at the same time as the Company RSU from which such Unvested Company RSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company RSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company RSU Consideration.

Each Vested Company PSU will, automatically and without any required action on the part of the holder thereof, be cancelled and converted into the right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Vested Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration, subject to any required withholding of taxes.

Each Unvested Company PSU will, automatically and without any required action on the part of the holder thereof, be converted into the contingent right to receive an amount in cash, without interest, equal to the product obtained by multiplying (x) the total number of shares of Proofpoint common stock underlying such Company PSU based on the attainment of the applicable performance metrics at the target level of performance, by (y) the Per Share Merger Consideration. Subject to the holder’s continued service with Parent and its affiliates (including the Surviving Corporation and its subsidiaries) through the applicable vesting dates, such Unvested Company PSU Consideration amounts will vest and be payable at the same time as the Company PSU from which such Unvested Company PSU Consideration was converted would have vested and been payable pursuant to its terms and, subject to certain exceptions, will otherwise remain subject to the same terms and conditions as were applicable to the underlying Unvested Company PSU immediately prior to the Effective Time with respect to the receipt of the Unvested Company PSU Consideration.

The Merger Agreement provides that, with respect to the Company ESPP, as soon as practicable (but in any event within five (5) business days) following the date of the Merger Agreement, the Board of Directors (or, if appropriate, any committee administering the Company ESPP) will adopt such resolutions or take such other actions as may be required so that (i) participation in the Company ESPP will be limited to those employees who are participants on the date of the Merger Agreement, (ii) participants may not increase their payroll deduction elections or rate of contributions from those in effect on the date of the Merger Agreement or make any separate non-payroll contributions to the Company ESPP on or following the date of the Merger Agreement, (iii) no offering period will be commenced after the date of the Merger Agreement, (iv) each then outstanding purchase right shall be exercised as of the earlier of (A) the end of the offering period in effect on the date of the Merger Agreement or (B) ten (10) days prior to the date on which the Effective Time occurs, and (v) the Company ESPP will terminate immediately prior to, but contingent upon the occurrence of, the Effective Time, but subsequent to the exercise of purchase rights on such purchase date (in accordance with the terms of the Company ESPP). On such exercise date, Proofpoint will apply the funds credited as of such date pursuant to the Company ESPP within each participant’s payroll withholding account to the purchase of whole shares of Proofpoint common stock in accordance with the terms of the Company ESPP and each share purchased thereunder immediately prior to the Effective Time will be canceled at the Effective Time and converted into the right to receive the Per Share Merger Consideration, subject to withholding of any applicable withholding taxes. Any accumulated contributions of each participant under the Company ESPP as of immediately prior to the Effective Time will, to the extent not used to purchase shares in accordance with the terms and conditions of the Company ESPP be refunded to such participant as promptly as practicable following the Effective Time (without interest).

The Merger Agreement provides that, on the Closing Date, Parent, Merger Sub and Proofpoint are required, as and to the extent required by the Convertible Notes Indenture (as defined in the section of this proxy statement captioned “—Financing of the Merger”), execute, and use reasonable best efforts to cause the trustee to execute, any supplemental indenture(s) required by the Convertible Notes Indenture and deliver any certificates and other

documents required by the Convertible Notes Indenture to be delivered by such persons in connection with such supplemental indenture(s). Proofpoint is required to use its reasonable best efforts to provide Parent and its counsel reasonable opportunity to review and comment on any notices, certificates, press releases, supplemental indentures, or other documents or instruments deliverable pursuant to the Convertible Notes Indenture prior to the dispatch or making thereof and to incorporate all reasonable comments provided by Parent and its counsel with respect thereto.

Prior to the Effective Time, Proofpoint is required to (i) use reasonable best efforts to facilitate the settlement of the Capped Call Transactions (as defined in the section of this proxy statement captioned “The Merger—Capped Call Transactions”) at or promptly following the Effective Time as reasonably requested by Parent and (ii) use reasonable best efforts to cooperate with Parent with respect to Parent’s efforts to negotiate any termination payments or valuations related to the settlement of the Capped Call Transactions that is effective at or after the Effective Time; provided that Proofpoint will not (x) agree to amend, modify or waive any terms relating to, or agree to any amount due upon the termination or settlement of, the Capped Call Transactions (except for amounts due upon exercise or termination of the Capped Call Transactions in accordance with their terms in connection with conversions of the Convertible Notes prior to the Effective Time) or (y) initiate or continue discussions or negotiations with the counterparties to the Capped Call Transactions or any of their respective affiliates or any other person regarding termination or settlement of the Capped Call Transactions without the prior written consent of Parent, and to the extent any such discussions or negotiations have occurred prior to date hereof, provide Parent with reasonable detail regarding the substance of all such discussions or negotiations and copies of any documentation sent or received in connection therewith (however, limitations in the immediately preceding clauses (x) and (y) will not apply to any modification, adjustment or termination made unilaterally by any of the counterparties to the Capped Call Transactions pursuant to the terms of the applicable Capped Call Confirmations (as defined in the section of this proxy statement captioned “The Merger—Capped Call Transactions”) or conditioned on termination or abandonment of the Merger Agreement); and nothing in the Merger Agreement requires Proofpoint to (A) make any payment with respect to the termination or settlement of any Capped Call Transaction as a result of the Merger prior to the occurrence of the Effective Time or (B) enter into any instrument or agreement relating to the termination or settlement of the Capped Call Transactions, or agree to any change or modification to any Capped Call Confirmations, that is effective prior to the Effective Time. Proofpoint is required to provide Parent with all written notices or other documents received by it with respect to any determination, cancellation, termination, exercise, settlement, adjustment or computation under, or in connection with any discussions or negotiations related to, the Capped Call Transactions and granted permission to Parent and its counsel and advisors to, at any time, initiate and engage in discussions and negotiations with the counterparties to the Capped Call Transactions regarding the settlement of the Capped Call Transactions at or promptly following the Effective Time and the terms of such settlement; provided that Proofpoint and its counsel will, to the extent reasonably practicable, have a reasonable opportunity to participate in such discussions and negotiations.

Prior to the Effective Time, Proofpoint is required to take all actions as may be required by the terms of the applicable Capped Call Transactions or applicable law, including the giving of any written notices or communication in connection with the Merger and/or any conversions and/or repurchases of the Convertible Notes or any adjustment under the Convertible Notes Indenture or occurring as a result of or in connection with the transactions contemplated by the Merger Agreement. Proofpoint is required to use its reasonable best efforts to provide Parent and its counsel reasonable time and opportunity to review any such written notice or communication prior to the dispatch or making thereof and shall incorporate all reasonable comments provided by Parent and its counsel with respect thereto.

Prior to the closing of the Merger, Parent will designate a U.S. bank or trust company, approved in advance by Proofpoint (the “Payment Agent”) to make payments of the Per Share Merger Consideration to Proofpoint Stockholders. At or prior to the Effective Time, Parent will deposit (or cause to be deposited) with the Payment Agent cash sufficient to pay the aggregate Per Share Merger Consideration to Proofpoint Stockholders.

As soon as reasonably practicable following the Effective Time (and in any event within five (5) business days), the Parent shall cause the Payment Agent to mail to each holder of record (as of immediately prior to the Effective Time) a letter of transmittal in customary form and instructions for use in effecting the surrender of such holder’s shares of Proofpoint common stock represented by such holder’s certificate(s) or book-entry shares

in exchange for the Per Share Merger Consideration payable in respect of such shares. The amount of any Per Share Merger Consideration paid to Proofpoint Stockholders may be reduced by any applicable withholding taxes.

The Merger Agreement contains representations and warranties of Proofpoint, Parent and Merger Sub.

Some of the representations and warranties in the Merger Agreement made by Proofpoint are qualified as to “materiality” or “Company Material Adverse Effect.” For purposes of the Merger Agreement, “Company Material Adverse Effect” means, with respect to Proofpoint, any event, change, occurrence, effect or development that, individually or taken together with all other events, changes, occurrences, effects or developments that occurred prior to the date of the occurrence of such an effect, is or would reasonably be expected to have a material adverse effect on the business, operations or financial condition of Proofpoint and its subsidiaries as a whole, or would reasonably be expected to prevent, materially impair or materially delay the consummation by Proofpoint of the Merger prior to the End Date, except that no events, changes, occurrences, effects or developments relating to or resulting from the following matters (by itself or when aggregated) will be deemed to be or constitute a Company Material Adverse Effect or will be taken into account when determining whether a Company Material Adverse Effect has occurred or would reasonably be expected to occur:

except, with respect to bullets 1, 3-4, and 8-11 above (other than, in the case of bullets 4 or 10, any change, event, effect or circumstance with respect to COVID-19 or the COVID-19 Measures or any escalation or worsening thereof (including any second or subsequent wave(s))) to the extent that such change, event, effect or circumstance has had a materially disproportionate adverse effect on Proofpoint and its subsidiaries, taken as a whole, relative to other companies operating in the industries in which Proofpoint and its subsidiaries operate, in which case only the incremental material and disproportionate adverse impact may be taken into account in determining whether there has occurred a Company Material Adverse Effect.

In the Merger Agreement, Proofpoint has made customary representations and warranties to Parent and Merger Sub that are subject, in some cases, to specified exceptions and qualifications contained in the Merger Agreement. These representations and warranties relate to, among other things:

In the Merger Agreement, Parent and Merger Sub have made customary representations and warranties to Proofpoint that are subject, in some cases, to specified exceptions and qualifications contained in the Merger Agreement. These representations and warranties relate to, among other things:

The representations and warranties contained in the Merger Agreement will not survive the consummation of the Merger.

During the period of time between the date of signing of the Merger Agreement and the first to occur of the Effective Time and the termination of the Merger Agreement (the “interim period”), except (i) as required by applicable law, (ii) as agreed in writing by Parent (which consent shall not be unreasonably withheld, delayed or conditioned); provided that Parent shall be deemed to have approved in writing if it provides no response within five (5) business days after written request by Proofpoint for such approval, (iii) as expressly required or permitted by the Merger Agreement or (iv) as disclosed in the confidential disclosure schedules to the Merger Agreement, Proofpoint shall, and shall cause its subsidiaries to:

During the interim period, except (i) as required by applicable law, (ii) as agreed in writing by Parent (which consent shall not be unreasonably withheld, delayed or conditioned); provided that Parent shall be deemed to have approved in writing if it provides no response within five (5) business days after written request by Proofpoint for such approval, (iii) as contemplated, required or permitted by the Merger Agreement, (iv) to the extent necessary to comply with the express obligations set forth in any material contract in effect on the date of the Merger Agreement, or (v) as disclosed in the confidential disclosure schedules to the Merger Agreement, Proofpoint will not, and will not allow its subsidiaries, as applicable to, among other things (and subject to certain exceptions):

Notwithstanding the restrictions set out above, nothing shall prevent Proofpoint or its subsidiaries from taking any action that would otherwise be prohibited reasonably in response to COVID-19 or any COVID-19 Measures so long as Proofpoint consults in good faith with Parent prior to taking such action.

In addition, from the date of the Merger Agreement until the earlier of the date the Merger Agreement is terminated and the expiration or termination of the waiting period under the HSR Act applicable to the Merger and the receipt of the required governmental consents, Parent and Merger Sub have agreed not to, and not to permit their equity investors or any of their subsidiaries or affiliates to, acquire or agree to acquire by merger or consolidation with, or by purchasing a material portion of the assets of or equity in, any person (a “Specified Acquisition”), if the entering into a definitive agreement with respect to or the consummation of a Specified Acquisition would reasonably be expected to (i) prevent, materially delay or materially impede the obtaining of the expiration or termination of the waiting period under the HSR Act applicable to the Merger and the receipt of governmental authority consents (or expiration of applicable waiting periods), or (ii) materially increase the risk of any governmental entity seeking or entering an order, ruling, judgment or injunction prohibiting the consummation of the transactions contemplated under the Merger Agreement.

Under the Merger Agreement, from the date of the Merger Agreement until the No-Shop Period Start Date, Proofpoint, its affiliates and their respective representatives have the right to: (i) solicit, initiate, propose, induce the making or submission of, encourage or facilitate in any way any offer or proposal that constitutes, or could reasonably be expected to lead to, an Alternative Acquisition Proposal (as defined in this section of this proxy statement below), including by providing information (including non-public information and data) relating to Proofpoint and any of its subsidiaries and affording access to the businesses, properties, assets, books, records or other non-public information, or to any personnel, of Proofpoint and its subsidiaries to any third person (and its representatives, including potential financing sources of the third person) that has entered into an Acceptable Confidentiality Agreement; provided that Proofpoint must provide Parent and Merger Sub (and their representatives, including financing sources) with access to any information or data that is provided to any third person given such access that was not previously made available (whether prior to or after the execution of the Merger Agreement) to Parent or Merger Sub substantially concurrently with the time it is provided to the third person (and in any event within 24 hours thereof) and (ii) continue, enter into, engage in or otherwise participate in any discussions or negotiations with any third person (and their respective representatives, including potential financing sources of the third person) regarding any Alternative Acquisition Proposals (or inquiries, offers or proposals or any other effort or attempt that could reasonably be expected to lead to an Alternative Acquisition Proposal), and cooperate with or assist or participate in, or facilitate in any way, any such inquiries, offers, proposals, discussions or negotiations or any effort or attempt to make any Alternative Acquisition Proposals or other proposals that could reasonably be expected to lead to Alternative Acquisition Proposals, including by granting a waiver, amendment or release under any pre-existing “standstill” or other similar provision to the extent necessary to allow for an Alternative Acquisition Proposal or amendment to an Alternative Acquisition Proposal to be made confidentially to Proofpoint or to the Board of Directors. Proofpoint must also notify Parent within 24 hours of entering into any Acceptable Confidentiality Agreement.

If Proofpoint terminates the Merger Agreement for the purpose of entering into a definitive agreement with any Excluded Party prior to the No-Shop Period Start Date in respect of a Superior Proposal, Proofpoint would be required to pay a termination fee of $122,982,000 to Parent. For more information, please see the section of this proxy statement captioned “—The Board of Directors’ Recommendation; Change of Recommendation.”

For purposes of this proxy statement and the Merger Agreement:

“Acceptable Confidentiality Agreement” means an agreement with Proofpoint that is either (i) in effect as of the date the Merger Agreement was entered into, or (ii) executed, delivered and effective after the date the Merger

Agreement was entered into, in either case containing provisions that require any counterparty thereto (and any of its affiliates and representatives named therein) that receive non-public information of or with respect to Proofpoint and/or its subsidiaries to keep such information confidential; provided, however, that, with respect to such agreements executed and delivered following the execution and delivery of the Merger Agreement, the provisions contained therein relating to the confidential treatment of information and the use thereof are no less restrictive in any material respect in the aggregate to such counterparty (and any of its affiliates and representatives named therein) than the terms of the confidentiality agreement entered into between Proofpoint and Thoma Bravo (it being understood that such agreement need not contain any “standstill” or similar provisions or otherwise prohibit the making of any Alternative Acquisition Proposal) and that such agreement does not contain provisions which prohibit Proofpoint from providing any information to Parent in accordance with the Merger Agreement.

“Alternative Acquisition Proposal” means any offer, proposal or indication of interest by a third person relating to or concerning (i) a merger, reorganization, share exchange, consolidation, tender offer, business combination, recapitalization, liquidation, dissolution or similar transaction involving Proofpoint, in each case, as a result of which Proofpoint Stockholders immediately prior to such transaction would cease to own at least 75% of the total voting power of Proofpoint or the surviving entity (or any direct or indirect parent company thereof), as applicable, immediately following such transaction, (ii) the direct or indirect acquisition by any third person of assets constituting or accounting for more than 25% of the consolidated assets, revenue or net income of Proofpoint and its subsidiaries, on a consolidated basis (including equity interests in any subsidiaries), or (iii) the direct or indirect acquisition by any third person of more than 25% of the outstanding shares of Proofpoint common stock or securities representing more than 25% of the total voting power of Proofpoint.

“Excluded Party” means any third person (i) from whom Proofpoint received a written Alternative Acquisition Proposal after the date of the Merger Agreement and prior to the No-Shop Period Start Date and (ii) whose Alternative Acquisition Proposal the Board of Directors determines in good faith prior to the start of the No-Shop Period Start Date, after consultation with its outside financial advisor and legal counsel, either to be a Superior Proposal or an Alternative Acquisition Proposal that would reasonably be expected to lead to a Superior Proposal; provided, however, that a third person will immediately cease to be an Excluded Party (and the provisions of the Merger Agreement applicable to Excluded Parties will cease to apply with respect to such third person) if (1) the Alternative Acquisition Proposal is withdrawn by the third person or (2) the Alternative Acquisition Proposal, in the good faith determination of the Board of Directors, after consultation with its outside financial advisor and legal counsel, no longer is or would no longer be reasonably expected to lead to a Superior Proposal.

“Superior Proposal” means a written Alternative Acquisition Proposal substituting in the definition thereof “80%” for “25%” and for “75%” in each place each such phrase appears, that (i) was not solicited in violation of the non-solicitation obligations pursuant to the Merger Agreement and (ii) the Board of Directors determines in good faith, after consultation with Proofpoint’s outside legal and financial advisors, and considering such factors as the Board of Directors considers to be appropriate (including (a) all legal, regulatory and financial aspects of the proposal (including certainty of closing) and the identity of the third person making the Alternative Acquisition Proposal and (b) any revisions to the Merger Agreement made or proposed in writing by Parent prior to the time of such determination in accordance with the change of recommendation provisions of the Merger Agreement), to be more favorable to Proofpoint and Proofpoint Stockholders than the transactions contemplated by the Merger Agreement.

From the date of the No-Shop Period Start Date until the earlier to occur of the termination of the Merger Agreement and the Effective Time, Proofpoint has agreed not to, and to cause its subsidiaries and its and their respective representatives not to, directly or indirectly:

In addition, Proofpoint has agreed to (i) cease and cause to be terminated any discussions or negotiations with any third person and its representatives, (ii) request the prompt return or destruction of all non-public information concerning Proofpoint and its subsidiaries furnished to any person with whom a confidentiality agreement with respect to an Alternative Acquisition Proposal was entered into at any time within twelve (12) months immediately preceding the No-Shop Period Start Date, (iii) cease providing any further information with respect to Proofpoint or any Alternative Acquisition Proposal to any such third person or its representatives and (iv) terminate all access granted to any such third person or its representatives to any physical or electronic data room (or any other diligence access).

Notwithstanding these restrictions, Proofpoint may continue to engage in the activities delineated in the previous two paragraphs with respect to any Excluded Party (but only for so long as such person is and remains an Excluded Party), including with respect to any amended or modified Alternative Acquisition Proposal received from any Excluded Party following the No-Shop Period Start Date.

Additionally, under certain specified circumstances, at any time prior to the adoption of the Merger Agreement by Proofpoint Stockholders, if Proofpoint receives an Alternative Acquisition Proposal from a third party that was not received in response to, or as a result of, any material breach of Proofpoint’s non-solicitation obligations pursuant to the Merger Agreement, (i) Proofpoint and its representatives may contact the third party making such Alternative Acquisition Proposal solely to clarify the terms and conditions thereof, and (ii) if the Board of Directors determines in good faith, after consultation with outside legal and financial advisors, that such Alternative Acquisition Proposal either constitutes a Superior Proposal or would reasonably be expected to lead to a Superior Proposal and the Board of Directors (or a committee thereof) has determined in good faith (after consultation with its financial advisor and outside legal counsel) that the failure to take the actions in respect of such Alternative Acquisition Proposal would be inconsistent with its fiduciary duties under applicable law, then Proofpoint may: (A) engage in discussions or negotiations with the third party (including its representatives and potential equity and debt financing sources) with respect to such Alternative Acquisition Proposal, and (B) furnish nonpublic information to the third party making such Alternative Acquisition Proposal (and its representatives and potential equity and debt financing sources) if, prior to so furnishing such information, the third party has executed an Acceptable Confidentiality Agreement with Proofpoint; provided that Proofpoint provides to Parent and Merger Sub (and their respective representatives) any information or data that is provided to such third party that was not previously made available to Parent or Merger Sub prior to or substantially concurrently with the time it is provided to such third party (and in any event within 24 hours thereof). Proofpoint will notify Parent that it has entered into an Acceptable Confidentiality Agreement within 24 hours after the execution thereof.

Both during the Go-Shop Period and after the No-Shop Period Start Date but prior to the adoption of the Merger Agreement by Proofpoint Stockholders, Proofpoint is not entitled to terminate the Merger Agreement for the purpose of entering into an agreement in respect of a Superior Proposal unless it complies with certain procedures in the Merger Agreement, including, but not limited to, negotiating with Parent in good faith over a five-(5)-business-day period in an effort to amend the terms and conditions of the Merger Agreement, so that such Superior Proposal no longer constitutes a “Superior Proposal” relative to the transactions contemplated by the Merger Agreement, as amended pursuant to such negotiations.

If Proofpoint terminates the Merger Agreement prior to the adoption of the Merger Agreement by Proofpoint Stockholders for the purpose of entering into an agreement in respect of a Superior Proposal, other than entering into an agreement in respect of a Superior Proposal with an Excluded Party prior to the No-Shop Period Start Date, Proofpoint must pay a $368,946,000 termination fee to Parent.

As described above, and subject to the provisions described below, the Board of Directors has made the recommendation that Proofpoint Stockholders vote “FOR” the proposal to adopt the Merger Agreement. The Merger Agreement provides that the Board of Directors will not effect a Change of Recommendation except as described below.

Prior to the adoption of the Merger Agreement by Proofpoint Stockholders, the Board of Directors may not take any action described in the following (any such action, a “Change of Recommendation”):

Nothing contained in the Merger Agreement prohibits Proofpoint or the Board of Directors from (i) complying with its disclosure obligations under applicable law or rules and policies of NASDAQ, including taking and disclosing to Proofpoint Stockholders a position contemplated by Rule 14d-9 or Rule 14e-2(a) or Item 1012(a) of Regulation M-A under the Exchange Act (or any similar communication to Proofpoint Stockholders) or from issuing a “stop, look and listen” statement pending disclosure of its position thereunder or (ii) making any disclosure to Proofpoint Stockholders if the Board of Directors determines in good faith, after consultation with the Company’s outside legal counsel, that the failure of the Board of Directors to make such disclosure would reasonably be expected to be inconsistent with the exercise of its fiduciary duties under applicable law; provided that (1) any such statement or disclosure must be subject to the terms and conditions of the Merger Agreement and will not limit or otherwise affect the obligations of Proofpoint or the Board of Directors and the rights of Parent under the applicable section of the Merger Agreement, and (2) nothing in the foregoing will be deemed to permit Proofpoint or the Board of Directors to effect a Change of Recommendation other than in accordance with the applicable section of the Merger Agreement.

Notwithstanding the restrictions described above, prior to the adoption of the Merger Agreement by Proofpoint Stockholders, the Board of Directors may effect a Change of Recommendation if (i) Proofpoint has received a Superior Proposal or (ii) there has been an Intervening Event (as defined herein), in each case, that the Board of Directors has determined in good faith (after consultation with its outside legal and financial advisors) that the failure to effect a Change of Recommendation would reasonably be expected to be inconsistent with its fiduciary duties under applicable law.

The Board of Directors may only effect a Change of Recommendation or authorize Proofpoint to terminate the Merger Agreement to enter into an agreement with respect to a Superior Proposal substantially concurrently with the termination of the Merger Agreement if:

In the event of any material amendments or modifications to such Alternative Acquisition Proposal, Proofpoint is required to deliver a new written notice to Parent and to comply with the requirements of the Merger Agreement with respect to such new written notice (it being understood that the five-(5)-business-day period shall be three (3) business days with respect to such new written notice, but in no event shorter than five (5) business days following the original written notice).

In addition, the Board of Directors may only effect a Change of Recommendation for an Intervening Event if:

For purposes of this proxy statement and the Merger Agreement, an “Intervening Event” means any event, change, occurrence or development that is unknown and not reasonably foreseeable to the Board of Directors as of the date of the Merger Agreement, or if known or reasonably foreseeable to the Board of Directors as of the date of the Merger Agreement, the material consequences of which were not known or reasonably foreseeable to the Board of Directors as of the date of Merger Agreement; provided that (a) the receipt, existence or terms of an Alternative Acquisition Proposal or Superior Proposal, or (b) the mere fact, in and of itself, that Proofpoint meets or exceeds any internal or published projections, forecasts, estimates or predictions of revenue, earnings or other financial or operating metrics for any period ending on or after the date of the Merger Agreement, or changes after the date of the Merger Agreement in the market price or trading volume of Proofpoint’s common stock or the credit rating of Proofpoint (it being understood that the underlying cause of any of the foregoing in this clause (b) may be considered and taken into account), in each case, shall not be deemed to be an Intervening Event under the Merger Agreement.

The Merger Agreement provides that from and after the Effective Time, Proofpoint will, and Parent will cause Proofpoint to, honor all Proofpoint employee plans in accordance with their terms. Parent acknowledges that a “change in control” (or similar phrase) will occur at the Effective Time for purposes of the employee plans.

For a period commencing at the Effective Time and ending on the earlier of (A) the first (1st) anniversary of the Effective Time and (B) the date of termination of the Company Employee, Parent will cause the Surviving Corporation or its affiliates to provide to each current employee of Proofpoint and its subsidiaries as of the Effective Time who remains so employed immediately after the Effective Time (“Company Employees”) (i) base compensation and target annual or short-term cash incentive opportunities (including target short-term commission-based cash incentive opportunities) that, in each case, are no less favorable than were provided to the Company Employee immediately before the Effective Time, and (ii) employee benefits (excluding equity and equity-based compensation) that are substantially comparable in the aggregate to those that were provided to the Company Employee immediately before the Effective Time.

For all purposes of vesting, eligibility to participate and level of benefits under the corresponding employee benefit plans of Parent and its subsidiaries providing benefits to any Company Employees after the Effective Time (the “New Plans”), each Company Employee will be credited with his or her years of service with Proofpoint and its subsidiaries and their respective predecessors before the Effective Time, to the same extent and for the same purpose as such Company Employee was entitled, before the Effective Time, to credit for such service under any similar Company Benefit Plan in which such Company Employee participated or was eligible to participate immediately prior to the Effective Time. However, the foregoing will not apply with respect to any defined benefit pension benefits or to the extent that its application would result in a duplication of benefits. In addition, and without limiting the generality of the foregoing, (i) each Company Employee will be immediately eligible to participate, without any waiting time, in any New Plans to the extent coverage under such New Plan is comparable to and replaces a Company Benefit Plan in which such Company Employee participated immediately before the Effective Time (such plans, collectively, the “Old Plans”), and (ii) for purposes of each New Plan providing medical, dental, pharmaceutical, and vision insurance benefits to any Company Employee, Parent will use commercially reasonable efforts to cause all preexisting condition exclusions and actively-at-work requirements of such New Plan to be waived for such employee and his or her covered dependents, unless such conditions would not have been waived or satisfied under the comparable plans of Proofpoint or its subsidiaries in which such employee participated immediately prior to the Effective Time, and Parent will cause any eligible expenses incurred by such employee and his or her covered dependents during the portion of the plan year of the Old Plans ending on the date such employee’s participation in the corresponding New Plan begins to be taken into account under such New Plan for purposes of satisfying the corresponding deductible, coinsurance and maximum out-of-pocket requirements applicable to such employee and his or her covered dependents for the applicable plan year as if such amounts had been paid in accordance with such New Plan to the extent such amounts were credited to such person for the same purpose under the Old Plan.

Under the Merger Agreement, Parent, Merger Sub and Proofpoint agreed to use, and agreed to cause their respective affiliates to use, reasonable best efforts to take all actions and assist and cooperate with the other parties, in each case as necessary, proper and advisable, pursuant to applicable law or otherwise to consummate the Merger.

Pursuant to the Merger Agreement, Parent shall use reasonable best efforts to, and shall cause its subsidiaries to use reasonable best efforts to take, or cause to be taken, all actions, and do, or cause to be done, all things necessary, proper or advisable to consummate the financing on the terms (including the market “flex” provisions) set forth in the Financing Letters.

If any portion of the Debt Financing becomes unavailable on the terms and conditions (including any applicable market “flex” provisions) contemplated by the Debt Commitment Letter and such portion is necessary to fund the Required Amount, Parent shall promptly notify Proofpoint and Parent shall use its reasonable best efforts to obtain alternative financing from the same or alternative sources in an amount sufficient to fund the Required Amount and with terms (taken as a whole) not less favorable to Parent (or its affiliates) than those set forth in the Debt Commitment Letter and which do not include any conditions to the consummation of such alternative financing that are more onerous than the conditions set forth in the Debt Commitment Letter.

In connection with the efforts of Parent and Merger Sub to arrange the financing, prior to the Closing Date, Proofpoint shall use its reasonable best efforts to provide, and to cause its subsidiaries to use their reasonable best efforts to provide, to Parent and Merger Sub, in each case at Parent’s sole cost and expense, such cooperation as is customary for financings of the type contemplated in the Debt Commitment Letter and reasonably requested by Parent in connection with the arrangement of the Debt Financing, including using its reasonable best efforts to, upon Parent’s written request and subject to certain exceptions set forth in the Merger Agreement: (i) furnish Parent (A) the unaudited condensed consolidated balance sheet of the Company, and the related unaudited condensed consolidated statements of operations and cash flows as of March 31, 2021, and (B) the unaudited condensed consolidated balance sheet of Proofpoint, and the related unaudited condensed consolidated statement of operations and cash flows for each subsequent fiscal quarter (other than a fiscal quarter that is a fiscal year-end) ending more than forty-five (45) days prior to the Closing Date; (ii) assist in preparation for and participate in a reasonable number of investor and lender meetings, presentations, road shows, due diligence sessions and sessions with rating agencies and accountants and assist with the marketing or syndication efforts of Parent in connection with the Debt Financing; (iii) facilitate the pledging of collateral of Proofpoint and its subsidiaries; (iv) to the extent reasonably requested by Parent no later than thirty (30) days prior to Closing with respect to any bank credit facility incurred after April 25, 2021, by Proofpoint or any of its subsidiaries, provide a customary payoff letter and lien terminations and instruments of discharge (to the extent applicable), in each case to be delivered at Closing to allow for the payoff, discharge and termination in full on the Closing Date of all such indebtedness and liens (if any), subject to the occurrence of the Closing Date; (v) assist Parent with the preparation by Parent and the lenders party to the Debt Commitment Letter of customary offering documents, lender presentations, private placement memoranda, bank information memoranda, syndication memoranda, ratings agency presentations and other customary marketing documents required in connection with the Debt Financing, including the execution and delivery of customary authorization and representation letters; (vi) cooperate with Parent to obtain reasonable and customary corporate and facilities credit ratings; (vii) cooperate with the due diligence of the lenders party to the Debt Commitment Letter, to the extent customary and reasonably requested; (viii) provide reasonable and customary assistance to assist Parent in producing the pro forma financial statements of Proofpoint and its subsidiaries required by the Debt Commitment Letter; (ix) execute and deliver as of (but not prior to) the closing of the Merger any pledge and security documents, other definitive financing documents, or other certificates or documents as may be reasonably requested by Parent and otherwise reasonably facilitate the pledging of collateral as of (but not prior to) the closing of the Merger; and (x) (A) so long as requested by Parent at least ten (10) days prior to the Closing Date, provide at least three (3) days prior to the Closing Date, all documentation and other information relating to Proofpoint or any of its subsidiaries required by bank regulatory authorities under applicable “know-your-customer” and anti-money laundering rules and regulations, including the USA Patriot Act, and

(B) if Proofpoint is a “legal entity” customer under 31 C.F.R. § 1010.230, so long as requested by Parent at least ten (10) business days prior to the Closing Date, provide at least three (3) business days prior to the Closing Date, a beneficial ownership certificate in relation to the Company.

Notwithstanding the foregoing, none of Proofpoint nor any of its affiliates shall be required to take or permit the taking of any action that would (i) require Proofpoint or its subsidiaries or any of their respective affiliates or any persons who are officers or directors of such entities to pass resolutions or consents to approve or authorize the execution of the Debt Financing, except those which are subject to the occurrence of the Closing passed by directors or officers continuing in their positions following the Closing, (ii) require Proofpoint or its subsidiaries or any of their respective affiliates or any persons who are officers or directors of such entities to enter into, execute or deliver any certificate, document, instrument or agreement or agree to any change or modification of any existing certificate, document, instrument or agreement, in each case, that is not contingent upon the Closing or that would be effective prior to the Closing (other than the execution of customary authorization letters and representation letters referenced above), (iii) cause any representation or warranty in the Merger Agreement to be breached by Proofpoint or any of its affiliates, (iv) require Proofpoint or any of its affiliates to pay any commitment or other similar fee or incur any other expense, liability or obligation in connection with the Debt Financing prior to the Closing or have any obligation of Proofpoint or any of its affiliates under any agreement, certificate, document or instrument be effective prior to the Closing, (v) cause any director, officer, employee of Proofpoint or Proofpoint Stockholder or any of Proofpoint’s affiliates to incur any personal liability, (vi) conflict with the organizational documents of Proofpoint or any of its affiliates or any laws, (vii) reasonably be expected to result in a violation or breach of, or a default (with or without notice, lapse of time, or both) under, any material contract to which Proofpoint or any of its affiliates is a party, (viii) provide access to or disclose information that Proofpoint or any of its affiliates reasonably determines would jeopardize any attorney-client privilege, or (ix) require Proofpoint to prepare any financial statements or information that are not available to it and prepared in the ordinary course of its financial reporting practice. Neither Proofpoint nor any affiliate of Proofpoint shall be required to be an issuer or other obligor with respect to the Debt Financing prior to the Closing.

Parent will (x) promptly, upon request by Proofpoint, reimburse Proofpoint or any of its affiliates for all reasonable and documented out-of-pocket costs incurred by them or their respective representatives in connection with the cooperation of Proofpoint and its representatives contemplated by the financing cooperation covenant in the Merger Agreement (it being understood that such reimbursement will not apply to any fees, costs and expenses incurred by, or on behalf of, Proofpoint in connection with its ordinary course financial reporting requirements); and (y) indemnify and hold harmless Proofpoint, its affiliates and their respective representatives from and against any and all losses, suffered or incurred by any of them in connection with the arrangement of the Debt Financing and any action taken by them at the request of Parent or its representatives and any information used in connection therewith, in each case other than to the extent any of the foregoing was suffered or incurred as a result of the bad faith, fraud, gross negligence or willful misconduct of Proofpoint, its affiliates and their respective representatives.

Parent, Merger Sub and Proofpoint have agreed that all indemnification or other similar agreements between any current or former directors, officers or employees, on the one hand, and Proofpoint or any of its subsidiaries, on the other hand, as in effect on the date of the Merger Agreement, will survive the Merger and remain in full force and effect in accordance with their respective terms. For a period of six (6) years after the Effective Time, Parent and the Surviving Corporation will maintain in effect the exculpation, indemnification and advancement of expenses provisions of the certificates of incorporation and bylaws or similar organizational documents of Proofpoint and of any subsidiaries as in effect immediately prior to the Effective Time, and will not amend, repeal or otherwise modify any such provisions in any manner that would adversely affect the rights thereunder of any individuals who at the Effective Time were current or former directors, officers or employees of Proofpoint or any of its subsidiaries; provided, however, that all rights to indemnification in respect of any actual or threatened claim, action, suit, proceeding or investigation, whether civil, criminal, administrative or investigative (a “Proceeding”), pending or asserted or any claim made within such period will continue until the final disposition of the Proceeding or resolution of such claim, even if beyond such six-(6)-year period. From and after the Effective Time, Parent will assume, be jointly and severally liable for, and honor, guarantee and stand surety for, and will cause the Surviving Corporation and its subsidiaries to honor, in accordance with their respective terms, the indemnification provisions of the Merger Agreement.

From and after the Effective Time, Parent and the Surviving Corporation will, to the fullest extent provided in the governing and organizational documents of Proofpoint and its subsidiaries and all indemnification or other similar agreements between any current or former directors, officers or employees, indemnify and hold harmless each present and former director, officer or employee of Proofpoint or any of its subsidiaries and any person who served as a director, officer, member, trustee or fiduciary of another corporation, partnership, joint venture, trust, pension or other employee benefit plan or enterprise at the request of or for the benefit of Proofpoint or its subsidiaries (each, an “Indemnified Party”) against any costs or expenses (including advancing reasonable attorneys’ fees and expenses), judgments, fines, losses, claims, damages, obligations, costs, liabilities and amounts paid in settlement in connection with a Proceeding, arising out of, relating to or in connection with any action or omission occurring or alleged to have occurred at or prior to the Effective Time (including acts or omissions in connection with such persons serving as an officer, director, employee or other fiduciary of any entity if such service was at the request or for the benefit of Proofpoint or its subsidiaries), whether asserted or claimed prior to, at or after the Effective Time, in all cases solely to the extent provided in the governing and organizational documents of Proofpoint and its subsidiaries. In the event of any such Proceeding, Parent and the Surviving Corporation will cooperate with the Indemnified Party in the defense of any such Proceeding.

In addition, prior to the Effective Time, Proofpoint will purchase a six-(6)-year “tail” insurance policy on Proofpoint’s current policies of directors’ and officers’ liability insurance on terms and conditions providing substantially equivalent benefits as the current policies of directors’ and officers’ liability insurance and fiduciary liability insurance maintained by Proofpoint and its subsidiaries with respect to matters arising on or before the Effective Time, including covering without limitation the transactions contemplated by the Merger Agreement; provided that the aggregate cost of such “tail” policy will not exceed 400% of the last annual premium paid by Proofpoint, and if the annual premium of such insurance coverage exceeds the maximum amount, Proofpoint, Parent, or the Surviving Corporation will only be required to obtain as much coverage as reasonably practicable for such amount. Parent and the Surviving Corporation will cause such policy to be maintained in full force and effect, for its full term, and cause all obligations thereunder to be honored by the Surviving Corporation, and no other party shall have any further obligation to purchase or pay for insurance under the indemnification provisions of the Merger Agreement.

Parent has also agreed to pay all reasonable expenses, including reasonable attorneys’ fees, that may be incurred by any Indemnified Party in enforcing the indemnity and other indemnification obligations provided in the Merger Agreement in the event Parent is found to have been in breach.

Proofpoint has agreed to take all necessary action (in accordance with applicable law and Proofpoint’s organizational documents) to establish a record date for, duly give notice of, convene and hold the Special Meeting as soon as reasonably practicable following the date upon which Proofpoint receives confirmation from the SEC that it will not review, or that it has completed its review of this proxy statement (which confirmation will be deemed to occur if the SEC has not affirmatively notified Proofpoint prior to the tenth (10^th) calendar day after filing this proxy statement that the SEC will or will not be reviewing this proxy statement).

Each of Proofpoint and Parent will keep the other reasonably informed of (including by providing copies of all pleadings), and cooperate with the other party in connection with, any stockholder litigation or claim against such party and/or its directors or officers relating to the Merger or the other transactions contemplated by the Merger Agreement. Proofpoint will: (i) give Parent a reasonable opportunity to participate in the defense or settlement of any such litigation or claim, (ii) consult in good faith with Parent with respect to the defense, settlement and prosecution of any such litigation or claim and (iii) not compromise or settle, or agree to compromise or settle, any stockholder litigation or claim arising or resulting from the transactions contemplated by the Merger Agreement without the prior written consent of Parent (such consent not to be unreasonably withheld, delayed or conditioned).

Prior to the Effective Time, without the prior written consent of Proofpoint, Parent will not permit or agree to permit any third person, other than the equity investors, to obtain any equity interests (or rights to obtain any

equity interests) in Parent or Merger Sub if such acquisition of equity interests or rights to obtain such equity interests would reasonably be expected to (i) delay in any material respect the obtaining of, or increase in any material respect the risk of not obtaining, any governmental consents necessary to consummate the transactions contemplated by the Merger Agreement or the expiration or termination of any applicable waiting period, (ii) increase in any material respect the risk of any governmental entity seeking or entering an order prohibiting the consummation of the transactions contemplated by Merger Agreement, or (iii) increase in any material respect the risk of not being able to remove any such order on appeal or otherwise.

The obligations of Parent and Merger Sub, on the one hand, and Proofpoint, on the other hand, to consummate the Merger are subject to the satisfaction or waiver (where permitted by applicable law) of each of the following conditions:

In addition, the obligations of Parent and Merger Sub to consummate the Merger are subject to the satisfaction or waiver (where permitted by applicable law) of each of the following additional conditions:

In addition, the obligation of Proofpoint to consummate the Merger is subject to the satisfaction or waiver (where permitted by applicable law) of each of the following additional conditions:

The Merger Agreement may be terminated at any time prior to the Effective Time, whether before or after the adoption of the Merger Agreement by Proofpoint Stockholders, in the following ways:

In the event that the Merger Agreement is terminated pursuant to the termination rights above, the Merger Agreement will be of no further force or effect without liability of any party to the other parties, as applicable, except certain sections of the Merger Agreement will survive the termination of the Merger Agreement in accordance with their respective terms. Notwithstanding the foregoing, nothing in the Merger Agreement will relieve any party from any liability for any fraud or willful and material breach of the Merger Agreement prior to its termination. In addition, no termination of the Merger Agreement will affect the rights or obligations of any party pursuant to the confidentiality agreement between Thoma Bravo and Proofpoint or the Guaranty, which rights, obligations and agreements will survive the termination of the Merger Agreement in accordance with their respective terms.

If Proofpoint terminates the Merger Agreement at any time prior to receipt of the approval of Proofpoint Stockholders for the purposes of entering into a definitive agreement with any Excluded Party prior to the No-Shop Period Start Date in respect of a Superior Proposal, Proofpoint would be required to pay a $122,982,000 termination fee to Parent. If the Merger Agreement is terminated under specified circumstances including the instances described below, Proofpoint must pay a $368,946,000 termination fee to Parent.

Parent will also be entitled to receive a termination fee of $368,946,000 from Proofpoint if the Merger Agreement is terminated:

Proofpoint will be entitled to receive a termination fee of $676,400,000 from Parent (the “Parent Termination Fee”) if the Merger Agreement is terminated:

Parent, Merger Sub and Proofpoint agree that irreparable damage for which monetary damages, even if available, would not be an adequate remedy would occur in the event that the parties do not timely perform the provisions of the Merger Agreement (including any party failing to take such actions as are required of it in order to consummate the Merger Agreement). Parent, Merger Sub and Proofpoint acknowledge and agree that, in the event of any breach or threatened breach by any other party of any covenant or obligation contained in the Merger Agreement: (i) the non-breaching party will be entitled (in addition to any other remedy to which they are entitled at law or in equity, including monetary damages), to obtain (A) a decree or order of specific performance to enforce the observance and performance of such covenant or obligation and (B) an injunction restraining such breach or threatened breach and (ii) the fees and expenses provisions of the Merger Agreement are not intended to and would not adequately compensate Proofpoint, on the one hand, or Parent and Merger Sub, on the other hand, for the harm that would result from a breach of the Merger Agreement, and will not be construed to diminish or otherwise impair in any respect any party’s right to an injunction, specific performance and other equitable relief; and (iii) the right of specific enforcement is an integral part of the Merger and without that right, neither Proofpoint nor Parent would have entered into the Merger Agreement.

It is explicitly agreed that, subject to the limitations of the next two sentences, Proofpoint will have the right to specific performance in connection with enforcing Parent’s and Merger Sub’s obligations to consummate the Merger and cause the financing to be funded (including to cause Parent to enforce the obligations of the Thoma Bravo Funds under the Equity Commitment Letter in order to cause the Equity Financing to be timely completed in accordance with and subject to the terms and conditions set forth in the Equity Commitment Letter) subject to the terms and conditions set forth therein and in the Merger Agreement. Notwithstanding anything to the contrary in the Merger Agreement, it is explicitly agreed that the right of Proofpoint to seek an injunction, specific performance or other equitable remedies in connection with enforcing Parent’s obligation to cause the Equity Financing to be funded to fund a portion of the amount required to consummate the Merger and to make all payments required to be made in connection therewith (but not the right of Proofpoint to seek such injunctions, specific performance or other equitable remedies for any other reason) shall be subject to the requirements that (i) all of the (x) joint conditions to Parent, Merger Sub and Proofpoint’s obligations to consummate the Merger and (y) conditions to Parent and Merger Sub’s obligations to consummate the Merger, in each case, have been satisfied (other than those conditions that by their terms are to be satisfied at the Closing, but subject to the satisfaction or waiver (to the extent permitted hereunder) of such conditions), (ii) the Debt Financing has been funded in accordance with the terms and conditions thereof or will be funded in accordance with the terms and

conditions thereof if the Equity Financing is funded, (iii) Proofpoint has irrevocably confirmed in writing that if the Equity Financing and Debt Financing are funded, then Proofpoint shall take such actions that are required of it by the Merger Agreement to consummate the closing of the Merger pursuant to the terms of the Merger Agreement and (iv) Parent and Merger Sub will have failed to consummate the Merger by the time Closing was to occur under the Merger Agreement. Notwithstanding the foregoing and subject to the rights of the parties to the definitive agreements for any financing under the terms thereof, Proofpoint is not entitled to directly seek the remedy of specific performance of the Merger Agreement against any debt financing source. Additionally, the election to pursue an injunction, specific performance or other equitable relief will not restrict, impair or otherwise limit Proofpoint from, in the alternative, seeking to terminate the Merger Agreement and collect the Parent Termination Fee; provided that in no event will Proofpoint be permitted to pursue an injunction, specific performance or other equitable relief or any other remedy under the Merger Agreement or available at law or equity following the payment of the Parent Termination Fee in accordance with the terms of the Merger Agreement.

Parent, Merger Sub and Proofpoint agree not to raise any objections to (i) the granting of an injunction, specific performance or other equitable relief to prevent or restrain breaches or threatened breaches of the Merger Agreement by Proofpoint, on the one hand, or Parent and Merger Sub, on the other hand; and (ii) the specific performance of the terms and provisions of the Merger Agreement to prevent breaches or threatened breaches of, or to enforce compliance with, the covenants, obligations and agreements of Parent and Merger Sub pursuant to the Merger Agreement. Any party seeking an injunction or injunctions to prevent breaches of the Merger Agreement and to enforce specifically the terms and provisions of the Merger Agreement will not be required to provide any bond or other security in connection with such injunction or enforcement, and each party irrevocably waives any right that it may have to require the obtaining, furnishing or posting of any such bond or other security.

The collective monetary damages of Parent, Merger Sub or any of their affiliates for breaches (including any willful breach) under the Merger Agreement (taking into account the payment of the Parent Termination Fee pursuant to the Merger Agreement), the Guaranty or the Equity Commitment Letter will not exceed, in the aggregate for all such breaches, an amount equal to $676,400,000 plus certain reimbursement obligations. The maximum aggregate monetary damages of Proofpoint for breaches under the Merger Agreement (taking into account the payment of the termination fee, if applicable) will not exceed an amount equal to $368,946,000 in the aggregate for all such breaches. Notwithstanding such limitations on liability for monetary damages, Parent, Merger Sub and Proofpoint may be entitled to an injunction, specific performance or other equitable relief as provided in the Merger Agreement.

Except in specified circumstances, whether or not the Merger is completed, all costs and expenses incurred in connection with the Merger and the other transactions contemplated by the Merger Agreement will be paid by the party incurring or required to incur such expenses, except that all filing fees paid by any party in respect of any and all filings under the antitrust and foreign investment laws shall be borne by Parent and that generally Parent will pay or cause to be paid all transfer, documentary, sales, use, stamp, registration, real property transfer and other similar taxes and fees imposed with respect to, or as a result of, entering into the Merger Agreement and completing the Merger and that such taxes and fees expressly will not be a liability of Proofpoint Stockholders or holders of Proofpoint equity awards.

The Merger Agreement may be amended by the parties in an executed written instrument at any time before or after adoption of the Merger Agreement by Proofpoint Stockholders. However, after adoption of the Merger Agreement by Proofpoint Stockholders, no amendment that requires further approval by such Proofpoint Stockholders pursuant to applicable law or in accordance with the rules and regulations of NASDAQ may be made without such approval.

The Merger Agreement is governed by Delaware law.

Proofpoint’s directors and officers, which collectively own 797,392 shares of Proofpoint common stock representing approximately 1.38% of the outstanding Proofpoint common stock as of June 3, 2021, have entered into the Voting Agreement with Parent and Proofpoint. A copy of the Voting Agreement is attached as Annex B and is incorporated herein by reference. Pursuant to the Voting Agreement, Proofpoint’s directors and officers have agreed, among other things, to (i) vote in favor of the proposal to adopt the Merger Agreement and (ii) vote against (x) any action or agreement that would reasonably be expected to result in any of the conditions of Proofpoint’s obligations set forth in the section of this proxy statement captioned “—Conditions to the Closing of the Merger” not being fulfilled and (y) any Alternative Acquisition Proposal, or any agreement, transaction or other matter that is intended to, or would reasonably be expected to, impede, interfere with or materially and adversely affect the consummation of the Merger and the other transactions contemplated by the Merger Agreement. The Voting Agreement shall terminate upon the earlier to occur of (a) the receipt of the affirmative vote for the proposal to adopt the Merger Agreement of the holders of at least a majority of the outstanding shares of Proofpoint common stock entitled to vote at the Special Meeting, (b) the Effective Time, (c) the termination of the Merger Agreement and (d) any amendment to the Merger Agreement that reduces the Per Share Merger Consideration or changes the form of consideration payable to Proofpoint Stockholders pursuant to the Merger Agreement (which would materially delay the Effective Time or is otherwise materially adverse to any Proofpoint Stockholders, in each case, without such Proofpoint Stockholders’ prior consent).

Subject to certain exceptions, Proofpoint’s directors and officers may not transfer their shares of Proofpoint common stock other than with the prior written consent of Parent.

The Board of Directors unanimously recommends that you vote “FOR” this proposal.