X0306 4 2015-03-12 0 0001212458 PROOFPOINT INC PFPT 0001547394 Knight David C/O PROOFPOINT, INC. 892 ROSS DRIVE SUNNYVALE CA 94089 0 1 0 0 EVP&GM, Info Security Products Common Stock 2015-03-12 4 M 0 10000 5.48 A 11561 D Common Stock 2015-03-12 4 S 0 2500 53.5896 D 9061 D Common Stock 2015-03-12 4 S 0 600 54.8683 D 8461 D Common Stock 2015-03-12 4 S 0 6500 55.9839 D 1961 D Common Stock 2015-03-12 4 S 0 400 56.4725 D 1561 D Non-qualified stock option (right to buy) 5.48 2015-03-12 4 M 0 10000 0 D 2021-04-29 Common Stock 10000 35752 D The transactions reported on this Form 4 were effected pursuant to a 10b5-1 trading plan adopted by the reporting person on November 11, 2013. 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 $53.07 to $54.00 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. Represents the weighted average sales price per share. The shares sold at prices ranging from $54.33 to $55.32 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 $55.40 to $56.39 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 $56.40 to $56.58 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. /s/ David Knight By Michael Yang, Attorney-In-Fact 2015-03-16