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                                                                    EXHIBIT 10.4

March 1, 2002

Thomas Oberdorf
49 Miller Circle
Armonk, NY 10504

Dear Tom:

It is a distinct pleasure to offer you the position of Chief Financial Officer
and Treasurer of CMGI, Inc. ("CMGI" or the "Company"). In this capacity you will
report to George McMillan, Chief Executive Officer, CMGI.

Your starting salary will be $12,500 bi-weekly, which is equivalent to an
annualized base salary of $325,000. You will also be eligible to receive a
pro-rated bonus for fiscal year 2002 based on a target annualized bonus of
$162,500. This bonus will be based on successful satisfaction of fiscal year
2002 business objectives pursuant to the terms and conditions of CMGI's FY 2002
Bonus Plan for CMGI Corporate. Your target annualized bonus for fiscal year 2002
will be 50% of your base salary.

You are eligible for relocation benefits up to a maximum of $150,000. These
benefits are outlined in CMGI's Relocation Policy, which is attached for your
reference. All relocation will be coordinated through MSI, the relocation vendor
for the Company. Please contact Joyce Fantasia to initiate the relocation
process. Should you take advantage of these benefits, and terminate either
voluntarily or for cause (as defined below), during the first year following
your effective date of hire, 100% of all funds provided to you for relocation
will be immediately repayable to the Company. If you terminate either
voluntarily or for cause during the second year following your effective date of
hire, 50% of the total funds provided to you will be immediately repayable to
the Company.

For purposes of this offer letter, "cause" shall mean a good faith finding by
the Company of: (i) gross negligence or willful misconduct by you in connection
with your employment duties, (ii) failure by you to perform your duties or
responsibilities required pursuant to your employment, after written notice and
an opportunity to cure, (iii) misappropriation by you of the assets or business
opportunities of the Company or its affiliates, (iv) embezzlement or other
financial fraud committed by you, (v) you knowingly allowing any third party to
commit any of the acts described in any of the preceding clauses (iii) or (iv),
or (vi) your indictment for, conviction of, or entry of a plea of no contest
with respect to, any felony.

In addition, on your start date, you will be granted an option to purchase
750,000 shares of CMGI common stock under the CMGI 2000 Stock Incentive Plan
(the "Plan"). This option will be priced at the closing price on the date of
grant and it will be divided into three tranches. The first tranche of the
option shall cover 350,000 shares and shall vest as follows: 25% on the earlier
to occur of (i) the first anniversary of the date of grant and (ii) the First
Confirmation Date (as defined below), and monthly thereafter commencing on the
13th monthly anniversary of the date of grant for the next three (3) years
(whereby 1/48th of the original number of the shares underlying the first
tranche of the option shall vest

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on each monthly anniversary date of the date of grant starting on the 13th
monthly anniversary date of the date of grant, until fully vested on the fourth
anniversary of the date of grant). The option shall have a seven (7) year term.

The second tranche of the option shall cover 250,000 shares and shall vest as
follows: 25% on the first anniversary of the First Confirmation Date and monthly
thereafter for the next three (3) years (whereby 1/48th of the original number
of the shares underlying the second tranche of the option shall vest on each
monthly anniversary date of the First Confirmation Date starting on the 13th
monthly anniversary date of the First Confirmation Date, until fully vested on
the fourth anniversary of the First Confirmation Date). Notwithstanding the
foregoing, in the event that the First Confirmation Date does not occur prior to
the fifth anniversary of the date of grant, the second tranche of the option
shall nonetheless become fully vested on such date. For purposes of this offer
letter, "First Confirmation Date" shall be defined as the first date following
the date of grant that CMGI publicly announces Net Operating Income (as defined
below) on a consolidated basis for a fiscal quarter commencing after the date of
grant greater than zero dollars.

The third tranche of the option shall cover 150,000 shares and shall vest as
follows: 25% on the first anniversary of the Second Confirmation Date (as
defined below) and monthly thereafter for the next three (3) years (whereby
1/48th of the original number of the shares underlying the option shall vest on
each monthly anniversary date of the Second Confirmation Date starting on the
13th monthly anniversary date of the Second Confirmation Date, until fully
vested on the fourth anniversary of the Second Confirmation Date).
Notwithstanding the foregoing, in the event that the Second Confirmation Date
does not occur prior to the fifth anniversary of the date of grant, the third
tranche of the option shall nonetheless become fully vested on such date. For
purposes of this offer letter, "Second Confirmation Date" shall be defined as
the first date following the First Confirmation Date that CMGI publicly
announces Net Operating Income on a consolidated basis for a fiscal quarter
greater than that reached on the First Confirmation Date. .

For purposes of this offer letter, "Net Operating Income" shall be defined as
operating income excluding expenses related to in-process research and
development, depreciation, restructuring, long-lived asset impairment and
amortization of intangible assets and stock-based compensation.

All options described above shall be subject to all terms, limitations,
restrictions and termination provisions set forth in the Plan and in the
separate option agreements (which shall be based upon the Company's standard
form option agreement) that shall be executed to evidence the grant of such
options. Enclosed you will find a copy of a Non-Competition Agreement, the
execution of which is required as a condition of the Company granting you an
option to purchase CMGI common stock and your employment with the Company.
Additionally, as a condition of employment with CMGI, you are required to
execute the enclosed Non-Disclosure and Developments Agreement.

As an employee of CMGI, you may participate in any and all bonus and benefit
programs that the Company establishes and makes generally available to its
employees from time to time, provided you are eligible under (and subject to all
provisions of) the plan documents governing those programs. Details of the
benefits offered will be reviewed with you in orientation on your first day of
employment.

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In accordance with current federal law, you will be asked to provide
documentation proving your eligibility to work in the United States. Please
review the enclosed Employment Eligibility Verification Form (Form I9) and the
list of acceptable documents that are required. You must bring this on your
first day of employment. If you fail to bring proper documentation with you on
your first day of work, you will be asked to go home to collect your paperwork.
Unfortunately, there can be no exceptions. If you do not bring proper
documentation, you will be considered ineligible for employment and CMGI will
not add you to its payroll until the required I9 documentation is received.

Please confirm your acceptance of this position and your start date by signing
one copy of this letter and returning it to me. Additionally, please complete,
sign and return the enclosed Employee Information sheet along with the Sexual
Harassment policy, Massachusetts Tax Form, W4, Direct Deposit Form and both
agreements that are enclosed. All documents along with one copy of your signed
offer letter must be returned by the end of business on Thursday, if you wish to
start the following Monday.

If you choose to fax the documents, please fax a copy of your signed offer
letter and all the enclosed documents to 978/684-3816 and bring the originals
with you on your first day. If you wish to overnight the original documents,
please mail one copy of your signed offer letter and the entire enclosed package
to CMGI Attention: Joyce Fantasia 100 Brickstone Square Andover, MA 01810.

Your employment with CMGI will be "at-will". This means that your employment
with CMGI may be terminated by either you or CMGI at any time and for any
reason, with or without notice. This offer expires as of the close of business
on Friday, March 8, 2002. This offer supersedes all prior offers, both verbal
and written. This letter does not constitute a guarantee of employment or a
contract.

Thomas, we are very pleased by the prospect of your addition to the CMGI team,
and we are confident that you will make a significant contribution to our future
success!

Sincerely,

/s/ Jeffrey Yanagi

Jeff Yanagi
Executive Vice President
Human Resources

/s/ Thomas Oberdorf
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THOMAS OBERDORF

March 4, 2002
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