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                                                                     Exhibit 4.2


                               FIRST AMENDMENT TO
                          FOURTH AMENDED AND RESTATED
                          INVESTORS' RIGHTS  AGREEMENT

          Pursuant to Section 3.8 of the Fourth Amended and Restated Investors'
Rights Agreement dated as of August 13, 1999 (the "Agreement"), between Kana
Communications, Inc., a Delaware corporation, (the "Company") and the various
other parties thereto, the Company and the holders of a majority of the
Registrable Securities (as defined in the Agreement) hereby amend the Agreement
as of                 , 2000, as provided below.

          1.  Registration Rights.  Section 1.1(g) of the Agreement shall be
              -------------------
amended in its entirety to read as follows:

                (g)  "Registrable Securities" means (i) Common Stock issuable
          or issued upon conversion of the Series A Preferred Stock, Series A1
          Preferred Stock, Series B Preferred Stock, Series B1 Preferred Stock,
          Series C Preferred Stock, Series C1 Preferred Stock, Series D
          Preferred Stock and Series D1 Preferred Stock, (ii) Common Stock
          issued to Mark Gainey and Michael Horvath (for purposes only of
          Sections 1.3, 1.7, 1.8, 1.10 and 3.8 of this Agreement), (iii) the
          Common Stock issuable or issued upon conversion of the Series A
          Preferred Stock (including the Series A1 Preferred Stock) issued upon
          exercise of two warrants held by Ragnild Horvath and the Beni M.
          Horvath Trust 1991, (iv) all shares held by the parties listed on
          Schedule B hereto acquired or to be acquired in connection with the
          ----------
          Company's acquisition of Connectify pursuant to the Plan of
          Reorganization, (v) all shares held by the parties listed on Schedule
                                                                       --------
          C hereto acquired or to be acquired in connection with the Company's
          -
          acquisition of Silknet Software Inc. ("Silknet") pursuant to an
          Agreement and Plan of Reorganization dated as of February 6, 2000
          between Silknet, the Company and Pistol Acquisition Corp., a wholly-
          owned subsidiary of the Company, and (vi) any Common Stock of the
          Company issued as (or issuable upon the conversion or exercise of any
          warrant, right or other security which is issued as ) a dividend or
          other distribution with respect to, or in exchange for or in
          replacement of the shares referenced in (i), (ii), (iii), (iv) and (v)
          above, excluding in all cases, however, any Registrable Securities
          sold by a person in a transaction in which such person's rights under
          this Section 1 are not assigned.

In addition, the preamble to the Agreement shall be amended in its entirety to
read as follows:

                THIS FOURTH AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT
          is made as of the 13th day of August 1999, by and among Kana
          Communications, Inc. a Delaware corporation, (the "Company"), the
          parties listed on Schedule A hereto (the "Existing Investors") and
                            ----------
          the parties listed on Schedule B (the "Connectify Stockholders") and
                                ----------
          Schedule C hereto (collectively with the Existing Investors and the
          ----------
          Connectify Stockholders, the "Investors").

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<PAGE>

          2.  Schedule C.  The Agreement is hereby amended such that Schedule A
              ----------
to this First Amendment to Fourth Investors' Rights Agreement is added to and
made a part of the Agreement as Schedule C to the Agreement.

          3.  Notwithstanding Sections 1 and 2 above, each person listed on
Schedule A hereto shall not be considered an Investor and shall not have any
rights, benefits or obligations under the Agreement, as amended, unless such
person has executed and delivered this First Amendment.  In addition, each
person listed on Schedule A hereto, upon executing and delivering this First
Amendment agrees to be bound by the terms, conditions, limitations and rights
imposed or granted by the Agreement.


          IN WITNESS WHEREOF, the parties have executed this First Amendment to
Fourth Investors' Rights Agreement as of the date first above written.



                                KANA COMMUNICATIONS, INC.


                                By_________________________________________
                                Name:
                                Title:



                                MARK S. GAINEY

                                ___________________________________________


                                [Signature page of First Amendment to Fourth
                                 Amended and Restated Investors' Rights
                                 Agreement]








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<PAGE>

                                DRAPER FISHER ASSOCIATES FUND IV, L.P.


                                ___________________________________________
                                Name:
                                Title:

                                DRAPER FISHER PARTNERS IV, LLC


                                ___________________________________________
                                Name:
                                Title:














                    [Signature page of First Amendment to
          Fourth Amended and Restated Investors' Rights Agreement]

                                       3
<PAGE>

                                BENCHMARK CAPITAL PARTNERS, L.P.
                                By:  Benchmark Capital Management Co., L.L.C.,
                                     its General Partner


                                ___________________________________________
                                Name:
                                Title:


                                BENCHMARK FOUNDERS' FUND, L.P.
                                By:  Benchmark Capital Management Co., L.L.C.,
                                     its General Partner


                                ___________________________________________
                                Name:
                                Title:










                    [Signature page of First Amendment to
          Fourth Amended and Restated Investors' Rights Agreement]

                                       4
<PAGE>

[Signature Page for new Investors]












                    [Signature page of First Amendment to
          Fourth Amended and Restated Investors' Rights Agreement]

                                       5
<PAGE>

                                   Schedule A
                                   ----------


                                       6