<PAGE>   1

                                                                     EXHIBIT 4.1

                                LOCK-UP AGREEMENT

                                January 18, 2000


FleetBoston Robertson Stephens Inc.
Merrill Lynch, Pierce, Fenner & Smith Incorporated
Salomon Smith Barney, Inc.
Bear Stearns & Company, Inc.
J.P. Morgan & Co. Inc.
     As Representatives of the Several Underwriters
c/o FleetBoston Robertson Stephens
555 California Street
San Francisco, CA  94104
Ladies and Gentlemen:

     The undersigned understands that you, as representatives of the several
underwriters (the "UNDERWRITERS"), propose to enter into an Underwriting
Agreement (the "UNDERWRITING AGREEMENT") with MyPoints.com, Inc. (the
"COMPANY"), providing for the public offering (the "PUBLIC OFFERING") by the
Underwriters, including yourselves, of shares of the Common Stock, par value
$0.001, of the Company (the "COMMON STOCK"), pursuant to the Company's
Registration Statement on Form S-1 to be filed with the Securities and Exchange
Commission on or about January 20, 2000 (the "REGISTRATION STATEMENT").

     In consideration of the Underwriters' agreement to purchase and make the
Public Offering of the Common Stock, and for other good and valuable
consideration, receipt of which is hereby acknowledged, the undersigned hereby
agrees, for a period of 90 days beginning February 15, 2000 (the "LOCK-UP
PERIOD"), not to offer to sell, contract to sell or otherwise sell, dispose of,
loan, pledge or grant any rights with respect to (collectively, a "DISPOSITION")
any shares of Common Stock, any options or warrants to purchase any shares of
Common Stock or any securities convertible into or exchangeable for shares of
Common Stock (collectively, "SECURITIES"), now owned or hereafter acquired
directly by the undersigned or with respect to which the undersigned has or
hereafter acquires the power of disposition, otherwise than (i) as a bona fide
gift or gifts, provided the donee or donees thereof agree to be bound by this
Lock-Up Agreement, (ii) as a distribution to limited partners or shareholders of
the undersigned, provided that the distributees thereof agree in writing to be
bound by the terms of this Lock-Up Agreement or (iii) with the prior written
consent of FleetBoston Robertson Stephens Inc. The foregoing restriction is
expressly agreed to preclude the holder of the Securities from engaging in any
hedging or other transaction which is designed to or reasonably expected to lead
to or result in a Disposition of Securities or to have the economic consequence
of a transfer of ownership of the Common Stock during the Lock-Up Period even if
such Securities would be disposed of by someone other than the undersigned. Such
prohibited hedging or other transactions would include without limitation any
short sale (whether or not against the box) or any purchase, sale or grant of
any right (including without limitation any put or call option) with respect to
any Securities or with respect to any security (other than a broad-based market
basket or index) that includes, relates to or derives any significant part of
its value from Securities. Notwithstanding the foregoing, this Lock-Up Agreement
does not prohibit the sale of shares of the Common Stock by the undersigned to
the Underwriters in the Public Offering.

     Furthermore, the undersigned hereby agrees and consents to the entry of
stop transfer instructions with the Company's transfer agent against the
transfer of the Securities held by the undersigned except in compliance with
this Lock-Up Agreement. In the event that the Registration Statement shall not
have been declared effective on or before February 29, 2000 this Lock-Up
Agreement shall be of no further force or effect.

     This agreement will be governed and construed in accordance with the laws
of the State of New York.


                                        Very truly yours,



                                        ----------------------------------------
                                                      (signature)


                                        Name:
                                             -----------------------------------


                                        Address:
                                                --------------------------------


                                                --------------------------------