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                                                                     EXHIBIT 4.3

                                 AMENDMENT NO. 2
                                       TO
                        PREFERRED STOCK RIGHTS AGREEMENT


        This Amendment No. 2 to Preferred Stock Rights Agreement (this
"Amendment") is dated as of November 18, 2003 between Critical Path, Inc. (the
"Company"), and Computershare Trust Company, Inc. (the "Rights Agent"), with
reference to the following:

        A. The Company and the Rights Agent entered into that certain Preferred
Stock Rights Agreement dated as of March 19, 2001, as amended by that certain
Amendment No. 1 to Preferred Stock Rights Agreement dated as of November 6, 2001
(the "Agreement").

        B. The Company desires to amend the Agreement in certain respects in
order to permit certain investors to purchase securities being offered by the
Company without causing such investors to become Acquiring Persons (as defined
in the Agreement) and thereby trigger the occurrence of a Distribution Date (as
defined in the Agreement).

        C. Under the Agreement, the Company and the Rights Agent may amend the
Agreement, at any time prior to a Distribution Date, which has yet to occur.

        NOW, THEREFORE, pursuant to Section 27 of the Agreement, the Company and
the Rights Agent hereby amend, effective upon the date hereof, the definition of
the term "Acquiring Person" set forth in Section 1(a) of the Agreement to read
in its entirety as follows:

               "(a) "ACQUIRING PERSON" shall mean any Person who or which,
together with all Affiliates and Associates of such Person, shall be the
Beneficial Owner of 15% or more of the Common Shares of the Company then
outstanding, but shall not include the Company, any Subsidiary of the Company or
any employee benefit plan of the Company or of any Subsidiary of the Company, or
any entity holding Common Shares for or pursuant to the terms of any such plan.
Notwithstanding the foregoing, no Person shall be deemed to be an Acquiring
Person as the result of an acquisition of Common Shares or Exchangeable Shares
by the Company which, by reducing the number of shares outstanding, increases
the proportionate number of shares beneficially owned by such Person to 15% or
more of the Common Shares of the Company then outstanding; provided, however,
that if a Person shall become the Beneficial Owner of 15% or more of the Common
Shares of the Company then outstanding by reason of share repurchases by the
Company and shall, after such share repurchases by the Company, become the
Beneficial Owner of any additional Common Shares of the Company (other than
pursuant to a dividend or distribution paid or made by (i) the Company on the
outstanding Common Shares in Common Shares or pursuant to a split or subdivision
of the outstanding Common Shares or (ii) Exchangeco on the outstanding
Exchangeable Shares in Exchangeable Shares or pursuant to a split or subdivision
of the outstanding Exchangeable Shares), then such Person shall be deemed to be
an Acquiring Person unless, upon becoming the Beneficial Owner of such
additional Common Shares of the Company, such Person does not beneficially own
15% or more of the Common Shares of the Company then outstanding.
Notwithstanding the foregoing:

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        (i) if the Company's Board of Directors determines in good faith that a
Person who would otherwise be an "Acquiring Person," as defined pursuant to the
provisions of this Section 1(a), has become such inadvertently (including,
without limitation, because (x) such Person was unaware that such Person
Beneficially Owned a percentage of the Common Shares of the Company that would
otherwise cause such Person to be an "Acquiring Person," as defined pursuant to
the provisions of this Section 1(a), or (y) such Person was aware of the extent
of the Common Shares of the Company such Person Beneficially Owned but had no
actual knowledge of the consequences of such Beneficial Ownership under this
Agreement) and without any intention of changing or influencing control of the
Company, and if such Person divested or divests as promptly as practicable a
sufficient number of Common Shares so that such Person would no longer be an
"Acquiring Person," as defined pursuant to the provisions of this Section 1(a),
then such Person shall not be deemed to be or to have become an "Acquiring
Person" for any purposes of this Agreement;

        (ii) if, as of the date of this Agreement, any Person is the Beneficial
Owner of 15% or more of the Common Shares of the Company outstanding, such
Person shall not be or become an "Acquiring Person," as defined pursuant to the
provisions of this Section 1(a), unless and until such time as such Person shall
become the Beneficial Owner of additional Common Shares of the Company (other
than pursuant to a dividend or distribution paid or made by (x) the Company on
the outstanding Common Shares in Common Shares or pursuant to a split or
subdivision of the outstanding Common Shares or (y) Exchangeco on the
outstanding Exchangeable Shares in Exchangeable Shares or pursuant to a split or
subdivision of the outstanding Exchangeable Shares), unless, upon becoming the
Beneficial Owner of such additional Common Shares of the Company, such Person is
not then the Beneficial Owner of 15% or more of the Common Shares of the Company
then outstanding; and

        (iii) the term "Acquiring Person" shall not mean:

                A. General Atlantic Partners 74, L.P., a Delaware limited
                partnership, GAP Coinvestment Partners II, L.P., a Delaware
                limited partnership, and GapStar, LLC, a Delaware limited
                liability company (referred to collectively with their
                respective Affiliates and Associates as "GAP") so long as GAP
                does not increase (other than an increase resulting solely from
                a reduction of the number of shares of outstanding Common Stock,
                including by reason of repurchases of Common Stock or
                Exchangeable Shares by the Company, or a dividend or
                distribution paid or made by the Company or Exchangeco on, or a
                split or subdivision of, any shares of their respective capital
                stock) its Beneficial Ownership of Common Stock to a percentage
                of the outstanding shares of Common Stock at any time that is
                greater than: (1) the percentage of the outstanding shares of
                Common Stock represented by the sum of (x) the shares as to
                which GAP has Beneficial Ownership



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                as of the close of business on November 18, 2003, assuming, for
                purposes of this calculation, all warrants and other securities
                convertible into or exercisable for Common Stock, or any other
                rights to purchase Common Stock, in all cases where held or
                enjoyed by GAP, are immediately convertible or exercisable, plus
                (y) the shares as to which GAP obtains (or is entitled to
                obtain) Beneficial Ownership directly from the Company pursuant
                to the consummation of the transactions described in that
                certain Convertible Note Purchase and Exchange Agreement (the
                "2003 Purchase Agreement"), dated November 18, 2003, by and
                among the Company and the "Coinvestors" party thereto,
                including, without limitation, the Issuable Shares and the
                Rights Shares (each as defined in the 2003 Purchase Agreement);
                or (2) such lesser percentage as to which GAP has Beneficial
                Ownership following any transfer of securities by GAP after
                consummation of the transactions described in the 2003 Purchase
                Agreement (except that this clause A shall pertain only until
                such time as GAP has Beneficial Ownership of less than fifteen
                percent (15%) of the outstanding shares of Common Stock);
                provided, that any shares of Common Stock Beneficially Owned by
                one or more officers or directors of the Company where (x) such
                officers or directors are also included within the term "GAP"
                and (y) such shares of Common Stock were distributed directly by
                the Company to such officers or directors as equity-based
                compensation, shall be excluded from the calculation of the
                Beneficial Ownership of GAP for purposes of the definition of
                "Acquiring Person" if the inclusion of such shares of Common
                Stock in such calculation, by itself, would otherwise cause GAP
                to be an Acquiring Person;

                B. Cenwell Limited, Campina Enterprises Limited, Great Affluent
                Limited, Lion Cosmos Limited and Dragonfield Limited (referred
                to collectively with their respective Affiliates and Associates
                as "Cenwell") so long as Cenwell does not increase (other than
                an increase resulting solely from a reduction of the number of
                shares of outstanding Common Stock, including by reason of
                repurchases of Common Stock or Exchangeable Shares by the
                Company, or a dividend or distribution paid or made by the
                Company or Exchangeco on, or a split or subdivision of, any
                shares of their respective capital stock) its Beneficial
                Ownership of Common Stock to a percentage of the outstanding
                shares of Common Stock at any time that is greater than: (1) the
                percentage of the outstanding shares of Common Stock represented
                by the sum of (x) the shares as to which Cenwell has Beneficial
                Ownership as of the close of business on November 18, 2003,
                assuming, for purposes of this calculation, all warrants and
                other securities convertible into or exercisable for Common
                Stock, or any other rights to purchase Common Stock, in all
                cases where



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<PAGE>

                held or enjoyed by Cenwell, are immediately convertible or
                exercisable, plus (y) the shares as to which Cenwell obtains (or
                is entitled to obtain) Beneficial Ownership directly from the
                Company pursuant to the consummation of the transactions
                described in the 2003 Purchase Agreement, including, without
                limitation, the Exchange Shares and the Rights Shares (each as
                defined in the 2003 Purchase Agreement); or (2) such lesser
                percentage as to which Cenwell has Beneficial Ownership
                following any transfer of securities by Cenwell after
                consummation of the transactions described in the 2003 Purchase
                Agreement (except that this clause B. shall pertain only until
                such time as Cenwell has Beneficial Ownership of less than
                fifteen percent (15%) of the outstanding shares of Common
                Stock); and

                C. Vectis CP Holdings, LLC (referred to collectively with its
                Affiliates and Associates as "Vectis") so long as Vectis does
                not increase (other than an increase resulting solely from a
                reduction of the number of shares of outstanding Common Stock,
                including by reason of repurchases of Common Stock or
                Exchangeable Shares by the Company, or a dividend or
                distribution paid or made by the Company or Exchangeco on, or a
                split or subdivision of, any shares of their respective capital
                stock) its Beneficial Ownership of Common Stock to a percentage
                of the outstanding shares of Common Stock at any time that is
                greater than: (1) the percentage of the outstanding shares of
                Common Stock represented by the sum of (x) the shares as to
                which Vectis has Beneficial Ownership as of the close of
                business on November 7, 2001 (if any), plus (y) the shares as to
                which Vectis obtains Beneficial Ownership directly from the
                Company pursuant to the consummation of the transactions
                described in that certain Stock and Warrant Purchase and
                Exchange Agreement (the "2001 Purchase Agreement"), dated
                November 7, 2001, by and among the Company and the "Purchasers"
                named therein, plus (z) the shares as to which Vectis obtains
                Beneficial Ownership directly from the Company pursuant to the
                rights offering for an aggregate amount up to $21,000,000 of
                Series E Preferred Stock of the Company pursuant to which the
                Company will distribute transferable rights to certain holders
                of Common Stock; or (2) such lesser percentage as to which
                Vectis has Beneficial Ownership following any transfer of
                securities by Vectis after consummation of the transactions
                described in the 2001 Purchase Agreement (except that this
                clause C. shall pertain only until such time as Vectis has
                Beneficial Ownership of less than fifteen percent (15%) of the
                outstanding shares of Common Stock); provided, that any shares
                of Common Stock Beneficially Owned by one or more officers or
                directors of the Company where (x) such officers or directors
                are also included within the term "Vectis" and (y) such shares
                of Common Stock were distributed



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<PAGE>

                directly by the Company to such officers or directors as
                equity-based compensation, shall be excluded from the
                calculation of the Beneficial Ownership of Vectis for purposes
                of the definition of "Acquiring Person" if the inclusion of such
                shares of Common Stock in such calculation, by itself, would
                otherwise cause Vectis to be an Acquiring Person."


        The undersigned officer of the Company, being an appropriate officer of
the Company and authorized to do so by resolution of the board of directors of
the Company, hereby certifies to the Rights Agent that this Amendment is in
compliance with the terms of Section 27 of the Agreement.

        This Amendment may be executed in any number of counterparts, each of
which shall be deemed an original, and all of which together shall constitute
one instrument.

        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first above written.



                                            CRITICAL PATH, INC.


                                            By: /s/ MICHAEL ZUKERMAN
                                                --------------------------------
                                            Name: Michael Zukerman
                                            Title: Senior Vice President


                                            COMPUTERSHARE TRUST COMPANY, INC.


                                            By: /s/ KELLIE GWINN
                                                --------------------------------
                                            Name: Kellie Gwinn
                                            Title: Vice President

                                            COMPUTERSHARE TRUST COMPANY, INC.


                                            By: /s/ MARGO ANKELE
                                                --------------------------------
                                            Name: Margo Ankele
                                            Title: Officer


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