X0306 4 2021-04-20 0 0001212458 PROOFPOINT INC PFPT 0001819243 Willy Ashan C/O PROOFPOINT, INC. 925 WEST MAUDE AVENUE SUNNYVALE CA 94085 0 1 0 0 EVP/GM-Sec Prd & Svc Grp Common Stock 2021-04-20 4 M 0 469 0.00 A 3909 D Common Stock 2021-04-20 4 F 0 163 130.01 D 3746 D Restricted Stock Units 0.00 2021-04-20 4 A 0 1875 0.00 A Common Stock 1875 1875 D Restricted Stock Units 0.00 2021-04-20 4 M 0 469 0.00 D Common Stock 469 1406 D Vesting of restricted stock units ("RSUs") earned by the Reporting Person on April 20, 2021 as determined by the Issuer's Board of Directors. Exempt transaction pursuant to Section 16b-3(e) - payment of exercise price or tax liability by delivering or withholding securities incident to the receipt, exercise or vesting of a security issued in accordance with Rule 16b-3. All of the shares reported as disposed of in this Form 4 were relinquished by the Reporting Person and cancelled by the Issuer in exchange for the Issuer's agreement to pay federal and state tax withholding obligations of the Reporting Person resulting from the vesting of RSUs. Each RSU represents a contingent right to receive 1 share of the Issuer's Common Stock upon settlement for no consideration. The RSUs vested as to 1/4 of the total number of shares subject to the award on April 20, 2021; an additional 1/4 of the total number of shares subject to the award will vest on each of January 1, 2022, January 1, 2023, and January 1, 2024, subject to the Reporting Person's continued service to the Issuer through such dates. Shares of the Issuer's common stock will be delivered to the Reporting Person following vesting. RSUs do not expire; they either vest or are canceled prior to vesting date. /s/ Ashan Willy, by Michael Yang, Attorney-in-Fact 2021-04-22