Stamps.com (STMP) 10-Q 2004 Q3 Quarterly report

Exhibit 32.3

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,

In connection with the Quarterly Report of Stamps.com Inc. (the "Company") on Form 10-Q for the period ending September 30, 2004 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), I, James A. Harper, Chief Accounting Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge:

          (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

          (2) The information contained in the Report fairly presents, in all material respects, the financial condition and result of operations of the Company.

/s/  JAMES A. HARPER       

James A. Harper

Chief Accounting Officer

November 8, 2004