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                                                                     EXHIBIT 5.1


                                 June 21, 2000


Critical Path, Inc.
320 First Street
San Francisco, California  94105


     Re: Registration Statement on Form S-3


Ladies and Gentlemen:


     We have examined the Registration Statement on Form S-3 (the "Registration
Statement") to be filed by you with the Securities and Exchange Commission on or
about the date hereof in connection with the registration for resale under the
Securities Act of 1933, as amended, of up to $300,000,000 principle amount of
its 5 3/4% Convertible Subordinated Notes due 2005 previously issued and
outstanding and the 2,956,380 (the "Notes") shares of your Common Stock issuable
thereunder (the "Conversion Shares") (together, the Notes and the Conversion
Shares are referred to as the "Securities"). As your legal counsel, we have also
reviewed the proceedings taken by you in connection with the issuance of the
Securities.


     It is our opinion that the Notes are legally issued and binding
obligations. Further, it is our opinion that the Common Stock issuable upon the
conversion of the Notes will be validly issued, fully-paid and non-assessable.


     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 the Prospectus constituting a part thereof,
and any amendments thereto.


                                         Very truly yours,


                                         /s/ WILSON SONSINI GOODRICH & ROSATI
                                         Professional Corporation