<PAGE>
EXHIBIT 5
HALE AND DORR LLP
Counsellors At Law
60 State Street, Boston, Massachusetts 02109
617-526-6000 * FAX 617-526-5000
December 21, 2000
CMGI, Inc.
100 Brickstone Square
Andover, Massachusetts 01810
Re: 2000 Stock Incentive Plan
Equilibrium 1995 Stock Option Plan
Ladies and Gentlemen:
We have assisted in the preparation of a Registration Statement on Form S-8 (the
"Registration Statement") to be filed with the Securities and Exchange
Commission under the Securities Act of 1933, as amended (the "Securities Act"),
relating to an aggregate of 15,523,007 shares of Common Stock, $.01 par value
per share (the "Shares"), of CMGI, Inc., a Delaware corporation (the "Company"),
issuable under the Company's above-referenced employee benefit plans
(collectively, the "Plans"). The Equilibrium 1995 Stock Option Plan was assumed
pursuant to the Agreement and Plan of Merger, dated as of December 14, 1999, by
and among the Company, TX Corp., a Delaware corporation and a wholly owned
subsidiary of the Company, and Equilibrium, a California corporation.
We have examined the Restated Certificate of Incorporation of the Company, as
amended to date, and the Amended and Restated By-Laws of the Company, and
originals, or copies certified to our satisfaction, of all pertinent records of
the meetings of the directors and stockholders of the Company, the Registration
Statement and such other documents relating to the Company as we have deemed
material for the purposes of this opinion.
In our examination of the foregoing documents, we have assumed the genuineness
of all signatures, the authenticity of all documents submitted to us as
originals, the conformity to original documents of all documents submitted to us
as copies, the authenticity of the originals of such latter documents and the
legal competence of all signatories to such documents.
We assume that the appropriate action will be taken, prior to the offer and sale
of the Shares in accordance with the Plans, to register and qualify the Shares
for sale under all applicable state securities or "blue sky" laws.
We express no opinion herein as to the laws of any state or jurisdiction other
than the state laws of The Commonwealth of Massachusetts, the Delaware General
Corporation Law statute and the federal laws of the United States of America.
Based upon and subject to the foregoing, we are of the opinion that the Shares
have been duly authorized for issuance and, when the Shares are issued and paid
for in accordance with the terms and conditions of the Plans, the Shares will be
validly issued, fully paid and nonassessable.
It is understood that this opinion is to be used only in connection with the
offer and sale of the Shares while the Registration Statement is in effect.
<PAGE>
Please note that we are opining only as to the matters expressly set forth
herein, and no opinion should be inferred as to any other matters.
We hereby consent to the filing of this opinion with the Commission as an
exhibit to the Registration Statement in accordance with the requirements of
Item 601(b)(5) of Regulation S-K under the Securities Act and to the use of our
name therein under the caption "Interests of Named Experts and Counsel." In
giving such consent, we do not hereby admit that we are in the category of
persons whose consent is required under Section 7 of the Securities Act or the
rules and regulations of the Commission.
Very truly yours,
/s/ HALE AND DORR LLP
HALE AND DORR LLP
