X0306 4 2016-02-01 0 0001212458 PROOFPOINT INC PFPT 0001547434 Steele Gary C/O PROOFPOINT, INC. 892 ROSS DRIVE SUNNYVALE CA 94089 1 1 0 0 Chief Executive Officer Common Stock 2016-02-01 4 M 0 15000 0 A 15001 D Common Stock 2016-02-01 4 M 0 10750 0 A 25751 D Common Stock 2016-02-01 4 F 0 13438 49.61 D 12313 D Restricted Stock Units 0 2016-02-01 4 M 0 15000 0 D Common Stock 15000 30000 D Restricted Stock Units 0 2016-02-01 4 M 0 10750 0 D Common Stock 10750 32250 D Vesting of restricted stock units ("RSUs") granted to the Reporting Person on March 17, 2014. Vesting of RSUs granted to the Reporting Person on March 24, 2015. 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 Reporting Person did not sell or otherwise dispose of any of the shares reported on this Form 4 for any reason other than to cover required taxes. 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 1/4th of the total number of shares on February 1, 2015 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. The RSUs vest as to 1/4th of the total number of shares on February 1, 2016 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/ Gary Steele by Michael Yang, Attorney-in-Fact 2016-02-03