X0306 4 2013-04-29 1 0001212458 PROOFPOINT INC PFPT 0001299074 Meritech Management Associates II L.L.C. 245 LYTTON AVENUE, SUITE 350 PALO ALTO CA 94301 0 0 1 0 0001299073 Meritech Capital Associates II L.L.C. 245 LYTTON AVENUE, SUITE 350 SUITE 200 PALO ALTO CA 94301 0 0 1 0 0001119133 MERITECH CAPITAL PARTNERS II LP 245 LYTTON AVENUE, SUITE 350 SUITE 200 PALO ALTO CA 94301 0 0 1 0 0001255154 MERITECH CAPITAL AFFILIATES II LP 245 LYTTON AVENUE, SUITE 350 SUITE 200 PALO ALTO CA 94301 0 0 1 0 0001130610 MCP ENTREPRENEUR PARTNERS II LP 245 LYTTON AVENUE, SUITE 350 SUITE 200 PALO ALTO CA 94301 0 0 1 0 0001255151 MADERA PAUL S 245 LYTTON AVENUE, SUITE 350 PALO ALTO CA 94301 0 0 1 0 0001255152 GORDON MICHAEL B 245 LYTTON AVENUE, SUITE 350 PALO ALTO CA 94301 0 0 1 0 Common Stock 2013-04-29 4 S 0 96770 18.6 D 2923962 I See footnote Common Stock 2013-04-29 4 S 0 2490 18.6 D 75236 I See footnote Common Stock 2013-04-29 4 S 0 740 18.6 D 22359 I See footnote Common Stock 2013-04-30 4 S 0 3924 18.5 D 2920038 I See footnote Common Stock 2013-04-30 4 S 0 101 18.5 D 75135 I See footnote Common Stock 2013-04-30 4 S 0 30 18.5 D 22329 I See footnote The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.50 to $19.04, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote 1 to this Form 4. The reported securities are held of record by Meritech Capital Partners II L.P. ("MCP II"). Meritech Capital Associates II L.L.C., the general partner of MCP II, has sole voting and dispositive power with respect to the securities held by MCP II. The managing member of Meritech Capital Associates II L.L.C. is Meritech Management Associates II L.L.C. Paul S. Madera and Michael B. Gordon, the managing members of Meritech Management Associates II L.L.C., share voting and dispositive power with respect to the shares held by MCP II. Such persons and entities disclaim beneficial ownership of the securities held by MCP II except to the extent of any pecuniary interest therein. The reported securities are held of record by Meritech Capital Affiliates II L.P ("MCA II"). Meritech Capital Associates II L.L.C., the general partner of MCA II, has sole voting and dispositive power with respect to the securities held by MCA II. The managing member of Meritech Capital Associates II L.L.C. is Meritech Management Associates II L.L.C. Paul S. Madera and Michael B. Gordon, the managing members of Meritech Management Associates II L.L.C., share voting and dispositive power with respect to the shares held by MCA II. Such persons and entities disclaim beneficial ownership of the securities held by MCA II except to the extent of any pecuniary interest therein. The reported securities are held of record by MCP Entrepreneur Partners II L.P ("MCPEP II"). Meritech Capital Associates II L.L.C., the general partner of MCPEP II, has sole voting and dispositive power with respect to the securities held by MCPEP II. The managing member of Meritech Capital Associates II L.L.C. is Meritech Management Associates II L.L.C. Paul S. Madera and Michael B. Gordon, the managing members of Meritech Management Associates II L.L.C., share voting and dispositive power with respect to the shares held by MCPEP II. Such persons and entities disclaim beneficial ownership of the securities held by MCPEP II except to the extent of any pecuniary interest therein. /s/ Joel Backman, by power of attorney for Meritech Management Associates II L.L.C. 2013-05-01 /s/ Joel Backman, by power of attorney for Meritech Management Associates II L.L.C., the managing member of Meritech Capital Associates II L.L.C. 2013-05-01 /s/ Joel Backman, by power of attorney for Meritech Management Associates II L.L.C., the managing member of Meritech Capital Associates II L.L.C., the general partner of Meritech Capital Partners II L.P. 2013-05-01 /s/ Joel Backman, by power of attorney for Meritech Management Associates II L.L.C., the managing member of Meritech Capital Associates II L.L.C., the general partner of Meritech Capital Affiliates II L.P. 2013-05-01 /s/ Joel Backman, by power of attorney for Meritech Management Associates II L.L.C., the managing member of Meritech Capital Associates II L.L.C., the general partner of MCP Entrepreneur Partners II L.P. 2013-05-01 /s/ Joel Backman, by power of attorney for Paul S. Madera 2013-05-01 /s/ Joel Backman, by power of attorney for Michael B. Gordon 2013-05-01