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                                                                     EXHIBIT 8.2

           FORM OF TAX OPINION OF ORRICK, HERRINGTON & SUTCLIFFE LLP


                                December __, 1999



ISOCOR
3420 Ocean Park Boulevard
Santa Monica, CA 90405

Attention:  Board of Directors

Ladies and Gentlemen:

               We have acted as counsel to ISOCOR ("ISOCOR"), a California
corporation, in connection with the contemplated merger (the "Merger") of
Initialize Acquisition Corp. ("Merger Sub"), a California corporation and a
wholly-owned subsidiary of Critical Path, Inc. ("Critical Path"), with and into
ISOCOR, pursuant to an Agreement and Plan of Merger dated as of October 20, 1999
(the "Merger Agreement") by and among ISOCOR, Merger Sub and Critical Path. You
have requested our opinion as to certain federal income tax matters relating to
the Merger. This opinion is being delivered to you pursuant to Section 6.1(d) of
the Merger Agreement. All capitalized terms used herein, unless otherwise
specified, have the meanings assigned to them in the Merger Agreement.

               In rendering our opinion, we have examined and relied upon the
accuracy and completeness of the facts, information, covenants and
representations contained in the registration statement relating to the Merger
on Form S-4 in the form filed with the Securities and Exchange Commission (the
"Registration Statement"), the Merger Agreement and such other documents and
corporate records as we have deemed necessary or appropriate for purposes of
this opinion. In addition, we have relied upon certain statements,
representations and agreements made by ISOCOR and Critical Path, including
representations set forth in the Officer's Certificates of ISOCOR and Critical
Path that were provided to us (the "Officers' Certificates"). Our opinion is
conditioned on, among other things, the initial and continuing accuracy of the
facts, information, covenants and representations set forth in the documents
referred to above and the statements, representations and agreements made by
ISOCOR, Critical Path, and others, including those set forth in the Officers'
Certificates. We have no reason to believe that such facts, information,
covenants and representations are not true, but have not attempted to verify
them independently and expressly disclaim an opinion as to their validity and
accuracy.

               In our examination, we have assumed the genuineness of all
signatures, the legal capacity of natural persons, the authenticity of all
documents submitted to us as originals, the conformity to original documents of
all documents submitted to us as certified or photostatic copies and the
authenticity of the originals of such documents. We also have assumed that the
transactions related to the Merger or contemplated by the Merger Agreement will
be consummated in accordance with such agreements and that all covenants
contained in the



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Board of Directors
ISOCOR
December __, 1999
Page 2

Merger Agreement (including exhibits thereto) and the Officers' Certificates
will be performed without waiver or breach of any material provision thereof.
Moreover, we have assumed that any representation or statement made "to the best
of knowledge" or similarly qualified is correct without such qualification.
Furthermore, we have assumed that the Merger qualifies as a statutory merger
under the laws of the State of California.

               The opinion expressed in this letter is based on the provisions
of the Internal Revenue Code of 1986, as amended, final, temporary and proposed
Treasury regulations promulgated thereunder and administrative and judicial
interpretations thereof, all as in effect as of the date hereof and all of which
are subject to change (possibly on a retroactive basis). No ruling from the
Internal Revenue Service (the "IRS") has been or will be sought on any issues
related to the Merger, and there can be no assurance that the IRS will not take
a contrary view. Although our opinion expressed in this letter represents our
best judgment as to such matters, our opinion has no binding effect on the IRS
or the courts.

               Based upon and subject to the foregoing, and subject to the
qualifications set forth herein, we are of the opinion that the discussion under
the heading "Material United States Federal Income Tax Consequences of the
Merger" contained in the Registration Statement, insofar as it relates to
statements of law and legal conclusions, is correct in all material respects.
Because this opinion is being delivered prior to the Effective Time of the
Merger, it must be considered prospective and dependent on future events. There
can be no assurance that changes in the law will not take place which could
affect the United States federal income tax consequences of the Merger or that
contrary positions may not be taken by the IRS.

               Except as set forth above, we express no opinion to any party as
to the tax consequences, whether federal, state, local or foreign, of the Merger
or of any transactions related to the Merger or contemplated by the Merger
Agreement. We are furnishing this opinion to you solely in connection with
the Registration Statement. We consent to the use of our name wherever appearing
in the Registration Statement with respect to the discussion of the material
federal income tax consequences of the Merger and to the filing of this opinion
as an exhibit to the Registration Statement. In giving this consent, we do not
thereby admit that we are in the category of persons whose consent is required
under Section 7 of the Securities Act of 1933, as amended, or the rules and
regulations of the Securities and Exchange Commission thereunder, nor do we
thereby admit that we are experts with respect to any part of such Registration
Statement within the meaning of the term "experts" as used in the Securities Act
of 1933, as amended, or the rules and regulations of the Securities and Exchange
Commission thereunder. We disclaim any obligation to update this opinion letter
for events occurring or coming to our attention after the date hereof.



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Board of Directors
ISOCOR
December __, 1999
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                                            Very truly yours,


                                            /s/
                                            ----------------------------------
                                            Orrick, Herrington & Sutcliffe LLP

