<PAGE>

                                                                   Exhibit 10(a)

January 8, 2004

Brian Sanders
(address intentionally omitted)

Dear Brian,

This letter reflects our mutual agreement regarding your leaving employment with
ADVO, Inc. We have agreed as follows:

1.       If you sign and return this Agreement, you will be entitled to the
         following severance benefits.

         -  You will be retained on the active payroll through March 31, 2004 to
            provide any transitional services as requested by ADVO, Inc.

         -  Your inactive pay status shall begin on April 1, 2004 and continue
            until March 31, 2006, unless you find other employment. During this
            period, medical, dental and life insurance will continue. All other
            fringe benefits will cease as of March 31, 2004.

         -  In accordance with plan provisions, you will not be eligible for
            2004 bonus or for any subsequent years.

         -  You will no longer be eligible to receive any grants of options. You
            will continue to vest all stock options already granted, according
            to their terms, as long as you remain on inactive pay status. After
            you leave such status, you will no longer vest any options and you
            will have three (3) months within which to exercise any vested
            options.

         -  You will receive Executive outplacement services a contracted with
            Drake Beam.

2.       If you obtain employment during your inactive pay status, you are
         required to notify ADVO, Inc. immediately. At such time, you will be
         paid in a lump sum payment the balance of the amounts unpaid under
         paragraph 1 above, less necessary withholding, and all benefits shall
         cease at that time.

3.       At the end of the transitional period, you will return to ADVO, Inc.
         company credit cards, and all other company property in your
         possession.

<PAGE>

4.       After your inactive pay status ends, ADVO, Inc. will not contest on the
         basis of termination, any application which you make for unemployment
         compensation at the appropriate agency as long as all other aspects of
         the application are accurate.

5.       Soon after your inactive pay period, you will receive notification of
         your right under COBRA legislation to elect continuation of group
         coverage under the Company's medical and/or dental plans. You will have
         up to thirty-one (31) days to convert your group basic and universal
         life insurance to an individual policy basis. You will receive the
         written COBRA notice from the Corporate Benefits Department and may
         inquire to them about details regarding these privileges at (860)
         285-6307.

6.       In consideration for the extra benefits and payments described in this
         letter, which are in addition to those to which you are contractually
         entitled, you hereby release, and forever discharge ADVO, Inc., its
         subsidiaries and affiliated corporations, and all of their past,
         present, and future directors, officers, agents, employees, and
         stockholders, and their respective successors, assigns, and legal
         representatives, of and from all claims of any kind, known or unknown,
         which you now have or ever had against them or any of them, including,
         without limitation claims relating to your employment by them or any of
         them and claims relating to the cessation of that employment,
         including, by way of example only, claims for wrongful discharge,
         breach of contract or other common law claims, or under any Federal,
         State or local statute or regulation including, but not limited to,
         Title VII of the Civil Rights Act of 1964 as Amended, 42 U.S.C. 2000e
         et. seq.; the Employee Retirement Income Security Act of 1974
         ("ERISA"), 29 U.S.C. 1001 et. seq.; the Age Discrimination in
         Employment Act as amended: 29 U.S.C. 621 et seq. and the Civil Rights
         Act of 1991, and any claims for attorney's fees, expenses, or costs of
         litigation. However, this release shall not apply to any claims arising
         after the date of your signing of this letter, nor shall it apply to
         any claims by you to enforce the provisions of this letter.

7.       Also in consideration for the extra benefits and payments described in
         this letter, you promise not to disparage or otherwise reflect
         negatively upon the Company, its personnel or its business practices.
         You also promise not to disclose the terms of this agreement to any
         other person or entity except for the tax authorities, and your
         immediately family, accountants and attorneys, each of whom you will
         advise of the confidential nature of this Agreement. Any violation of
         this provision shall be a material breach of this agreement and will be
         grounds for its unilateral termination by the Company.

8.       ADVO agrees not to disparage or reflect negatively upon you and your
         service with ADVO. All job reference requests should be directed by
         Gary Mulloy or Ed Harless, and all responses shall be positive.

9.       This agreement supersedes all other agreements or understandings,
         written or oral that you have with ADVO.

<PAGE>

10.      You acknowledge that you have read this agreement carefully and fully
         understand its terms. BY THIS LETTER, YOU ARE BEING ADVISED TO SEEK
         COUNSEL AND, BY SIGNING BELOW, YOU ACKNOWLEDGE THAT YOU HAVE HAD THE
         OPPORTUNITY TO DO SO, AND ARE EXECUTING THIS AGREEMENT VOLUNTARILY AND
         KNOWINGLY.

11.      Please signify your acceptance of this agreement by signing and
         returning a copy to me. You have up to twenty-one (21) days to sign
         this agreement and return it to me. Thereafter, you may revoke your
         acceptance by sending me notice in writing within seven (7) days after
         you sign this letter. This letter will become a legally binding
         document only if the seven (7) day revocation period passes and you
         have not revoked your agreement as described in the preceding sentence.

I will serve as your point of contact regarding all provisions of this
agreement, including without limitation, medical benefits and expenses to assure
timely and prompt payment to you.

If you have any questions about this letter, please discuss them with me
promptly.

Sincerely,

/s/ EDWIN HARLESS
--------------------
Edwin L. Harless

                                     Agreed and accepted this

                                     12 of January, 2004

                                     /s/ BRIAN SANDERS
                                     ------------------------
                                     Brian Sanders