X0306 4 2018-08-01 0 0001212458 PROOFPOINT INC PFPT 0001410972 Auvil Paul R. III C/O PROOFPOINT, INC. 892 ROSS DRIVE SUNNYVALE CA 94089 0 1 0 0 Chief Financial Officer Common Stock 2018-08-01 4 M 0 3479 5.48 A 79528 D Common Stock 2018-08-01 4 M 0 19969 7.98 A 99497 D Common Stock 2018-08-01 4 S 0 18999 112.5853 D 80498 D Common Stock 2018-08-01 4 S 0 21001 114.7088 D 59497 D Common Stock 446398 I By family trust Employee Stock Option (right to buy) 5.48 2018-08-01 4 M 0 3479 0 D 2021-04-29 Common Stock 3479 0 D Employee Stock Option (right to buy) 7.98 2018-08-01 4 M 0 19969 0 D 2022-01-23 Common Stock 19969 5000 D Restricted Stock Units 0 Common Stock 50000 50000 D The transaction reported on this Form 4 was effected pursuant to a 10b5-1 trading plan adopted by the reporting person on June 4, 2018. Represents the aggregate of sales effected on the same day at different prices. Represents the weighted average sales price per share. The shares sold at prices ranging from $112.26 to $113.08 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. Represents the weighted average sales price per share. The shares sold at prices ranging from $114.14 to $115.00 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer. The stock option is immediately exercisable in full. Each restricted stock unit ("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 in equal annual installments beginning on June 1, 2019. Shares of the Issuer's common stock will be delivered to the Reporting Person following vesting. These RSUs were previously reported as common stock and are now being reported in Table II as derivative securities. /s/ Paul R. Auvil III by Michael Yang, Attorney-In-Fact 2018-08-03