Exhibit 5.1 ----------- October 14, 1999 E-Stamp Corporation 2855 Campus Drive, Suite 100 San Mateo, California 94403 Re: Registration Statement on Form S-8 ---------------------------------- Ladies and Gentlemen: We have examined the Registration Statement on Form S-8 (the "Registration Statement") to be filed by you with the Securities and Exchange Commission on or about October 14, 1999 (the "Registration Statement") in connection with the registration under the Securities Act of 1933, as amended (the "Securities Act"), of 3,978,463 shares of your Common Stock reserved for issuance under your 1996 Non-Employee Director Stock Option Plan, 1996 Stock Option and Restricted Stock Plan, 1999 Employee Stock Purchase Plan, 1999 Director Option Plan and 1999 Stock Plan (the "Plans"). As your legal counsel, we have examined the proceedings taken and are familiar with the proceedings proposed to be taken by you in connection with the sale and issuance of the Common Stock under the Plans. It is our opinion that, when issued and sold in the manner referred to in the Plans and pursuant to the agreements which accompany the Plans, the Common Stock issued and sold thereby will be legally and validly issued, fully paid and nonassesable. We consent to the use of this opinion as an exhibit to the Registration Statement and further consent to the use of our name wherever appearing in the Registration Statement, including any Prospectuses constituting a part thereof, and any amendments thereto. This opinion may be incorporated by reference in any abbreviated registration statement filed pursuant to Item E under the general instructions to Form S-8 under the Securities Act of 1933 with respect to the Registration Statement. Very truly yours, WILSON SONSINI GOODRICH & ROSATI Professional Corporation /s/ Wilson Sonsini Goodrich & Rosati