1
                                                                     EXHIBIT 5.1


                                 June 15, 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 914,652 previously issued and
outstanding shares of your Common Stock (the "Shares"). As your legal counsel,
we have also reviewed the proceedings taken by you in connection with the
issuance of the Shares.


     It is our opinion that the Shares are 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