X0306 4 2021-02-01 0 0001212458 PROOFPOINT INC PFPT 0001819243 Willy Ashan C/O PROOFPOINT, INC. 892 ROSS DRIVE SUNNYVALE CA 94089 0 1 0 0 EVP/GM-Sec Prd & Svc Grp Common Stock 2021-02-01 4 M 0 2250 0.00 A 4216 D Common Stock 2021-02-01 4 M 0 1875 0.00 A 6091 D Common Stock 2021-02-01 4 F 0 1425 130.62 D 4666 D Common Stock 2021-02-02 4 S 0 1226 136.38 D 3440 D Restricted Stock Units 0.00 2021-02-01 4 M 0 2250 0.00 D Common Stock 2250 4500 D Restricted Stock Units 0.00 2021-02-01 4 M 0 1875 0.00 D Common Stock 1875 5625 D Vesting of restricted stock units ("RSUs") previously granted to the Reporting Person. 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. The transactions reported on this Form 4 were effected pursuant to a 10b5-1 trading plan previously adopted by the reporting person. Each RSU represents a contingent right to receive 1 share of the Issuer's Common Stock upon settlement for no consideration. The RSUs vest as to 1/3 of the total RSUs in equal installments, with the first 1/3 vesting on February 1, 2021. 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 the vesting date. The RSUs vested as to 1/4th of the total number of shares on February 1, 2021 and thereafter will vest as to 1/4th of the total number of shares in equal annual installments. Shares of the Issuer's common stock will be delivered to the Reporting Person following vesting. /s/ Ashan Willy, by Michael Yang, Attorney-in-Fact 2021-02-03