Document:

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                                                                   EXHIBIT 4.2.1

                                 AMENDMENT NO. 1
                                       TO
                              AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

        This AMENDMENT NO. 1 TO AMENDED AND RESTATED REGISTRATION RIGHTS
AGREEMENT (the "AGREEMENT") is made as of the fourth day of January, 2000 by and
among Commtouch Software Ltd., an Israeli company (the "COMPANY") having its
principal executive offices at 6 Harzoran Street, Poleg Industrial Park,
P.O. Box 8511, Netanya 42504, Israel, and the investors identified on the
signature page to this Agreement (collectively, the "PREFERRED SHAREHOLDERS").

        In accordance with the provisions of Section 7 of the Amended and
Restated Registration Rights Agreement (the "RIGHTS AGREEMENT"), which provides
that any provision of the Rights Agreement may be amended, and the exercise of
any rights under the Rights Agreement may be waived (either generally or in a
particular instance, and either retroactively or prospectively) only with the
written consent of the Company, and at least a 75% majority in interest of the
holders of the Shares (as defined in the Rights Agreement), the parties to this
Agreement hereby agree as follows:

        1. The undersigned Preferred Shareholders constitute a 75% majority in
interest of the holders of the Shares (as defined in the Rights Agreement).

        2. The Company and the Preferred Shareholders hereby retroactively waive
the application of the provisions of the Rights Agreement to the issuance of all
of the ordinary shares purchased by each of Go2Net, Inc. and Vulcan Ventures,
Incorporated on July 16, 1999, Microsoft Corporation on December 29, 1999 and
the warrant issued to Go2Net, Inc. on July 16, 1999 and the registration
statement filed in connection therewith.

        3. The Company and the Preferred Shareholders hereby amend and restate
Section 7 of the Rights Agreement in its entirety as follows:

               "Any provision of these registration rights may be amended, and
        the exercise of any rights under this Agreement may be waived (either
        generally or in a particular instance, and either retroactively or
        prospectively) only with the written consent of the Company, and a 51%
        majority in interest of the holders of the Shares, except that any party
        may waive as to itself the exercise of any rights under this Agreement."

        4. This Agreement shall be governed by the laws of Israel, with any
terms relating to United States securities laws to be interpreted in accordance
with the federal laws of the United States of America. Any dispute arising,
under or with respect to this Agreement shall be resolved exclusively in the
appropriate court in Tel-Aviv, Israel.

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        5. This Agreement and the Rights Agreement shall constitute the entire
agreement among the parties regarding the transactions contemplated herein and
therein, and may not be amended except in writing. Except as set forth herein,
all of the terms of the Rights Agreement shall remain unchanged and be in full
force and effect and are hereby ratified and confirmed in all respects. In the
event of any conflict between the provisions of this Agreement and the Rights
Agreement, the provisions of this Agreement shall control. On and after the date
hereof, each reference in the Rights Agreement to "this Agreement," "hereunder,"
"hereof," "herein" or words of like import shall mean and be a reference to the
Rights Agreement as amended hereby.

        6. This Agreement may be executed in one or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

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        IN WITNESS WHEREOF, the parties have executed this Amendment No. 1 to
Amended and Restated Registration Rights Agreement as of the date first above
written.

COMMTOUCH SOFTWARE LTD.

        By: ___________________________
        Name: _________________________
        Title: ________________________

PREFERRED SHAREHOLDERS:

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

        By: ___________________________
        Name: _________________________
        Company: ______________________
        Title: ________________________

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                                                                  Exhibit 10.9.2

                                     WARRANT

        THE SECURITIES REPRESENTED BY THIS INSTRUMENT AND THE ORDINARY SHARES OF
        COMMTOUCH SOFTWARE, LTD. ISSUABLE UPON EXERCISE OF THIS WARRANT HAVE
        BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN CONNECTION
        WITH, THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR DISPOSITION MAY
        BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO
        OR AN OPINION OF COUNSEL REASONABLY ACCEPTABLE TO THE COMPANY THAT SUCH
        REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT OF 1933, AS
        AMENDED.

                                     WARRANT
                         To Purchase Ordinary Shares of
                            COMMTOUCH SOFTWARE, LTD.

This Warrant (the "WARRANT") certifies that, for value received, Microsoft
Corporation (the "HOLDER"), is entitled, upon the terms and subject to the
conditions hereinafter set forth, at any time on or after October 26, 1999 (the
"ISSUANCE DATE") and on or prior to December 29, 1999. but not thereafter, to
subscribe for and purchase from Commtouch Software, Ltd., an Israeli corporation
(the "COMPANY"), up to $20,000,000 worth of the Company's duly authorized,
validly issued, fully paid and non-assessable Ordinary Shares (the "WARRANT
SHARES") at an exercise price (the "EXERCISE PRICE") of $28.25 per share
(CLOSING PRICE ON OCTOBER 26, 1999).

THE TERMS, CONDITIONS AND INSTRUCTIONS TO THIS WARRANT ARE AS FOLLOWS:

1.      EXERCISE OF WARRANT

        1.1 GENERAL. The purchase rights represented by this Warrant are
exercisable by the Holder, in whole only, at any time and from time to time
prior to 5:00 p.m. December 29, 1999 (the "EXPIRATION DATE").

        1.2 METHOD OF EXERCISE. Subject to Section 10.8 and compliance with all
applicable federal and state securities laws, the purchase right represented by
this Warrant may be exercised, in whole only and from time to time, by the
Holder by: (i) surrender of this Warrant and delivery of the Notice of Exercise
(the form of which is attached hereto), duly executed, at the principal office
of the Company; and (ii) payment to the Company of an amount equal to the
aggregate Exercise Price pursuant to one of the payment methods permitted under
Section 2.3. Upon receipt by the Company of the foregoing items, the Company
shall promptly issue and deliver to the Holder a certificate for the Warrant
Shares so purchased. The Warrant Shares so purchased shall be deemed to be
issued to such Holder as the record owner of such shares as of the close of
business on the date on which this Warrant shall have been exercised as
aforesaid. Certificates

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for the Warrant Shares purchased hereunder shall be delivered to the Holder
within a reasonable time, but not later than 10 days after the date on which
this Warrant shall have been exercised as aforesaid.

        1.3 PAYMENT. Payment shall be made either: (a) by check drawn on a
United States bank and for United States funds made payable to the Company; or
(b) by wire transfer of United States funds for the account of the Company.

        1.4 NO FRACTIONAL SHARES OR SCRIP. No fractional shares or scrip
representing fractional shares shall be issued upon the exercise of this
Warrant.

        1.5 CHARGES, TAXES AND EXPENSES. Issuance of certificates for Warrant
Shares upon the exercise of this Warrant shall be made without charge to the
Holder for any issue or transfer tax or other incidental expense in respect of
the issuance of such certificate, all of which taxes and expenses shall be paid
by the Company, and such certificates shall be issued in the name of the holder.

        1.6 TRANSFER RESTRICTION LEGEND. This Warrant and each certificate for
Warrant Shares issued upon exercise of this Warrant, unless at the time of
exercise such shares are registered under the Securities Act of 1933, as
amended, (the "SECURITIES ACT"), shall bear the legend set forth on the first
page of this Warrant.

        1.7 CHARACTER OF WARRANT SHARES. All Warrant Shares issuable upon the
exercise of the Warrants, when issued, shall be duly authorized, validly issued,
fully paid and nonassessable.

2.      NO RIGHTS AS A SHAREHOLDER

        This Warrant by itself does not entitle the Holder to any voting rights
or other rights as a shareholder of the Company prior to the exercise hereof.

3.      ADJUSTMENT OF WARRANT PRICE AND NUMBER OF WARRANT SHARES PURCHASABLE

        If the Company at any time, by subdivision, combination or
reclassification of securities or otherwise, changes any of the securities to
which purchase rights under this Warrant exist into the same or a different
number of securities of any class or classes, this Warrant shall thereafter be
to acquire such number and kind of securities as would have been issuable as the
result of such change with respect to the securities which were subject to the
purchase rights under this Warrant immediately prior to such subdivision,
combination, reclassification or other change. If Ordinary Shares of the Company
are subdivided or combined into a greater or smaller number of Ordinary Shares,
the Exercise Price shall be proportionately reduced in the case of subdivision
of shares or proportionately increased in the case of combination of shares, in
both cases by the ratio which the total number of Ordinary Shares to be
outstanding immediately after such event bears to the total number of Ordinary
Shares outstanding immediately prior to such event.

4.      EXCHANGE AND REGISTRY OF WARRANT

        The Company shall maintain at its principal office a registry showing
the name and address of the registered holder of this Warrant. This Warrant may
be surrendered for exchange or exercise, in accordance with its terms, at such
office of the Company, and the Company shall be entitled to rely in all
respects, prior to written notice to the contrary, upon such registry.

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5.      LOSS, THEFT, DESTRUCTION OR MUTILATION OF WARRANT

        Upon receipt by the Company of evidence reasonably satisfactory to it of
the loss, theft, destruction or mutilation of this Warrant, and in case of loss,
theft or destruction, of indemnity or security reasonably satisfactory to it,
and upon reimbursement to the Company of all reasonable expenses incidental
thereto, and upon surrender and cancellation of this Warrant, if mutilated, the
Company will make and deliver a new Warrant of like tenor dated as of such
cancellation, in lieu of this Warrant.

6.      SATURDAYS, SUNDAYS, HOLIDAYS, ETC.

        If the last or appointed day for the taking of any action or the
expiration of any right required or granted herein shall be a Saturday or a
Sunday or shall be a legal holiday, then such action may be taken or such right
may be exercised on the next succeeding day not a Saturday, Sunday or legal
holiday.

7.      RESTRICTION ON TRANSFER

        This Warrant is not transferable. The Holder of this Warrant, by
acceptance hereof, agrees that, absent an effective registration statement under
the Securities Act covering the disposition of the Warrant Shares issued or
issuable upon exercise hereof such Holder will not sell or transfer any or all
of the Warrant Shares issuable upon exercise hereof without first: (a) providing
the Company, upon request, with an opinion of counsel (which may be counsel for
the Company) to the effect that such sale or transfer will be exempt from, or
complies with, the registration and prospectus delivery requirements of the
Securities Act and (b) consenting to the Company making a notation on its
records giving instructions to any transfer agent of the Warrant Shares in order
to implement such restriction on transferability.

8.      INVESTMENT REPRESENTATIONS

        This Warrant is being issued to the Holder in reliance upon the
representations and warranties that the Holder is purchasing this Warrant and
the Warrant Shares for its own account, for investment and with no present
intention of distributing or reselling any portion of this Warrant or the
Warrant Shares, but without prejudice to its right at all times to sell or
otherwise dispose of all or part of the Warrant Shares under an effective
registration exemption available under the Securities Act and either in
compliance with the registration or qualification requirements of any applicable
state securities law or under an exemption thereto.

9.      NOTICE OF ACTIONS

        In case at any time: (a) the Company shall declare or pay any dividend,
payable in stock or otherwise, upon any class of capital stock or declare or
make any other distribution to the holders of its capital stock; (b) the Company
shall propose to offer for subscription pro rata or otherwise to the holders of
any class of capital stock any additional shares of stock of any class or any
other rights; (c) there is any reorganization or merger of the Company with, or
transfer of all or substantially all of its assets to, another corporation; or
(d) there is a voluntary or involuntary dissolution, liquidation or winding up
of the Company, then, in any one or more of said cases, the Company shall give
written notice to the Holder of the date: (A) on which the books of Company
shall close, or of the record date fixed, for determining the shareholders
entitled to such dividend, distribution or subscription rights or (B) on which
such reorganization,

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reclassification, consolidation, merger, transfer, dissolution, liquidation or
winding up shall take place. Such notice shall also specify the date as of which
the holders of record of capital stock shall participate in such dividend,
distribution or subscription rights, or shall be entitled to exchange their
capital stock for securities or other property deliverable upon such
reorganization, reclassification, merger, transfer, dissolution, liquidation or
winding up, as the case may be. Such written notice shall be given at least 10
days prior to the record date or the date on which the Company's transfer books
are closed in respect thereto and the date fixed for determining the
shareholders entitled to such dividend, distribution, subscription right or
foreboding on such matter. If the Holder determines not to exercise prior to an
event described in this Section 9, an equitable adjustment shall be made to the
composition of this Warrant by reason of the proposed issuance, distribution or
other event, whether or not notice thereof has been given the Holder pursuant to
the provisions of this Section 9.

10.     MISCELLANEOUS

        10.1 ISSUE DATE. The provisions of this Warrant shall be construed and
shall be given effect in all respects as if it had been issued and delivered by
the Company on the Issuance Date hereof. This Warrant shall be binding upon any
successors or assigns of the Company.

        10.2 RESTRICTIONS. The Holder acknowledges that the Warrant Shares
acquired upon the exercise of this Warrant shall have restrictions on their
resale imposed by state and federal securities laws.

        10.3 AUTHORIZED SHARES. The Company covenants that during the period
this Warrant is outstanding, it will reserve from its authorized and unissued
Ordinary Shares a sufficient number of shares to provide for the issuance of the
Warrant. The Company further covenants that its issuance of this Warrant shall
constitute full authority to its officers who are charged with the duty of
executing stock certificates to execute and issue the necessary certificates for
Ordinary Shares upon the exercise of the purchase rights under this Warrant. The
Company covenants that all Ordinary Shares which may be issued upon the exercise
of rights represented by this Warrant, upon exercise of the rights represented
by this Warrant, shall be duly authorized, validly issued, fully paid and
nonassessable and free from all taxes, liens, and charges in respect of the
issue thereof (other than taxes in respect of any transfer occurring
contemporaneously with such issue).

        10.4 NO IMPAIRMENT. The Company will not, by amendment of its Memorandum
of Association or a ny other voluntary action, avoid or seek to avoid the
observance or performance of any of the terms of this Warrant, but will at all
times in good faith assist in the carrying out of all such terms and in the
taking of all such action as may be necessary or appropriate in order to protect
the rights of the holder hereof against impairment.

        10.5 OWNERSHIP OF WARRANT. The Company may deem and treat the registered
Holder as the true, lawful and absolute owner thereof for all purposes, and the
Company shall not be affected by any notice to the contrary.

        10.6 NOTICES. Any written notice required by the provisions of this
Warrant to be given by the Company to the Holder shall be validly given if given
personally or by mail or other means of written communication to the Holder in a
manner which would be sufficient to constitute the giving of valid notice of a
shareholders meeting were the Holder a shareholder of the Company. Any written
notice required by the provisions of this Warrant to be given by the

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Holder to the Company shall be in writing and shall be deemed to have been duly
given if personally delivered or if mailed by postage prepaid to the address of
the Company as provided herein or, if by fax, upon confirmation of transmission,
or, if sent by overnight courier service, on the following business day. The
addresses to which notice is to be given hereunder may be changed from time to
time by the parties entitled to notice by notice given as provided herein.

        10.7 GOVERNING LAW; CONSTRUCTION. This Warrant shall constitute a
contract under the laws of the State of California and for all purposes shall be
construed in accordance with and governed by the laws of said state, without
regard to any principles of choice of law or conflicts of law. The descriptive
headings of the several sections of this Warrant are inserted for convenience
only and shall not control or affect the meaning or construction of any of the
provisions thereof.

        10.8 EXPIRATION. This Warrant shall be void and all rights represented
thereby shall cease unless exercised on or before 5:00 p.m., Pacific Standard
Time, on the Expiration Date. All restrictions set forth herein on the shares of
capital stock issued upon exercise of any rights hereunder shall survive such
exercise and expiration of the rights granted hereunder.

        IN WITNESS WHEREOF, the Company has caused this Warrant to be executed
by its officer thereunto duly authorized.

Dated:  October 26, 1999

COMPANY:                                    COMMTOUCH SOFTWARE, LTD.

                                            /s/ GIDEON MANTEL
                                            ------------------------------------
                                            Gideon Mantel
                                            Chief Executive Officer

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                               NOTICE OF EXERCISE

To:     COMMTOUCH SOFTWARE, LTD.

        (1) The undersigned hereby elects to purchase 707,965 Ordinary Shares of
Commtouch Software, Ltd. (the "COMPANY") pursuant to the terms of the attached
warrant (the "Warrant"), and tenders herewith payment of the purchase price in
full, together with all applicable transfer taxes, if any.

        (2) The undersigned elects to pay for the purchase price as follows:

               By cash, check or wire transfer   $20,000,000.00

        (3) Please issue a certificate or certificates representing said
Ordinary Shares in the name of the undersigned.

        (4) The undersigned represents that the aforesaid Ordinary Shares are
being acquired for the account of the undersigned for investment and not with a
view to, or for resale in connection with, the distribution thereof and that the
undersigned has no present intention of distributing or reselling such shares.

----------------------                         --------------------------------
        (Date)                                           (Signature)

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