EXHIBIT 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350

AS ADOPTED PURSUANT TO SECTION 906

OF THE SARBANES-OXLEY ACT OF 2002

I, Gary Steele, Chief Executive Officer of Proofpoint, Inc. (the “Company”), do hereby certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

• the Annual Report on Form 10-K of the Company for the year ended December 31, 2012 (the "Report") fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

• the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company for the periods presented therein.

Date: March 8, 2012

/s/ GARY STEELE

Gary Steele

Chief Executive Officer

(Principal Executive Officer)

A signed original of this written statement required by Section 906 has been provided to Proofpoint, Inc. and will be retained by it and furnished to the Securities and Exchange Commission or its staff upon request.