X0306 4 2020-07-08 0 0001212458 PROOFPOINT INC PFPT 0001547434 Steele Gary C/O PROOFPOINT, INC. 892 ROSS DRIVE SUNNYVALE CA 94089 1 1 0 0 Chairman and CEO Common Stock 2020-07-08 4 S 0 901 113.5109 D 67947 D Common Stock 2020-07-08 4 S 0 9099 114.3786 D 58848 D The transactions reported on this Form 4 were effected pursuant to a 10b5-1 trading plan previously adopted by the reporting person. Represents the aggregate of sales effected on the same day at different prices. Represents the weighted average sale price. The lowest price at which shares were sold was $113.01 and the highest price at which shares were sold was $114.01. The reporting person undertakes to provide upon request to the staff of the Securities Exchange Commission, the issuer or its stockholders, full information regarding the total number of shares sold at each separate price within the ranges set forth in footnotes (3) and (4) to this Form 4. Represents the weighted average sale price. The lowest price at which shares were sold was $114.04 and the highest price at which shares were sold was $114.83. /s/ Gary Steele, by Michael Yang, Attorney-in-Fact 2020-07-09