<PAGE>   1


                                                                   EXHIBIT 10.5

                                                INTEROFFICE COMMUNICATION

[AETNA LOGO]

                                                ELEASE E. WRIGHT
                                                Senior Vice President
                                                Corporate Human Resources, RC3A
                                                (860) 273-8371
                                                Fax:  (860) 560-8721

To            Thomas J. McInerney

Date          June 26, 2000

Subject       Special Severance Arrangements

This memorandum is to outline special severance arrangements for you. This
memorandum is intended to replace your letter agreement dated April 6, 1999
which is hereby terminated. Notwithstanding the provisions in this memorandum,
you remain an employee-at-will of Aetna Inc. or one of its subsidiaries or
affiliates ("the Company") and the Company may terminate your employment at any
time with or without cause or notice.

In the event that a Change in Control (as defined below) occurs and that during
the two year period following such Change in Control (i) your employment is
involuntarily terminated for any reason other than gross misconduct in the
performance of your duties, (ii) you terminate your employment as a result of a
reduction made to your base salary (such termination to be made within 30 days
of such reduction) or (iii) you terminate your employment as a result of the
Company's relocation of your office 100 miles or more from your then current
office (such termination to be made within 30 days of such relocation), you
will be entitled to 156 weeks continuation of your cash compensation
(calculated at base salary and annual bonus opportunity for target-level
performance of 80% of base salary) in lieu of any severance or salary
continuation benefit to which you may otherwise have been entitled and without
any duplication of benefits upon delivery to the Company of a release of any
employment-related claims in the Company's customary form. For these purposes,
a Change in Control is described in Attachment A and incorporated herein.

In consideration of the foregoing, you agree that you will be subject to the
Company's Change in Control Excise Tax Policy for Selected Officers (the
"Policy"). You have received a memorandum describing the Policy and understand
and agree that application of this Policy may cause a reduction in the amount
payable to you hereunder and/or a cancellation or delay in the vesting of
awards you have received or may receive under the Company's compensation plans
and programs (e.g., stock options, ACEShares, etc.) (collectively, the
"Compensation Plans"). The terms of the Policy are incorporated herein by
reference and shall have the effect of amending any contrary terms of this
agreement, any Compensation Plan and any agreement under any Compensation Plan.

In the event your employment is involuntarily terminated by the Company (i) for
any reason not involving misconduct, and (ii) paragraph 2 above is not
applicable, you will be entitled instead to 52 weeks (or, if greater, the
number of weeks of salary continuation and severance payable under the
Company's Severance and Salary Continuation Benefits Plan then in effect)
continuation of


<PAGE>   2

Page 2
Thomas J. McInerney
June 26, 2000

your cash compensation (calculated at base salary and annual bonus opportunity
for target-level performance of 80% of base salary) in lieu of any severance or
salary continuation benefit to which you may otherwise be entitled upon
delivery to the Company of a release of any employment-related claims in the
Company's customary form.

Please signify your receipt and agreement to the foregoing by signing and
returning a copy of this memorandum to me.

Aetna Inc.                                           Agreed:


By:  /s/ Elease E. Wright                            /s/ Thomas J. McInerney
     ------------------------------------            ---------------------------
                                                     Thomas J. McInerney

                                                     Date:    July 11, 2000
                                                            --------------------

Att:  1 (Definition of Change in Control)

Enc:  1 (Excise Tax Policy for Selected Officers)


<PAGE>   3

                                                                   ATTACHMENT A

"Change in Control" means the happening of any of the following:

    (i)   When any "person" as defined in Section 3(a)(9) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act") and as used in Sections
13(d) and 14(d) thereof, including a "group" as defined in Section 13(d) of the
Exchange Act but excluding Aetna Inc. (the "Company") and any subsidiary
thereof and any employee benefit plan sponsored or maintained by the Company or
any subsidiary (including any trustee of such plan acting as trustee), directly
or indirectly, becomes the "beneficial owner" (as defined in Rule 13d-3 under
the Exchange Act, as amended from time to time), of securities of the Company
representing 20 percent or more of the combined voting power of the Company's
then outstanding securities;

    (ii)  When, during any period of 24 consecutive months, the individuals
who, at the beginning of such period, constitute the Company's Board of
Directors (the "Incumbent Directors") cease for any reason other than death to
constitute at least a majority thereof, provided that a director who was not a
director at the beginning of such 24-month period shall be deemed to have
satisfied such 24-month requirement (and be an Incumbent Director) if such
director was elected by, or on the recommendation of or with the approval of,
at least two-thirds of the directors who then qualified as Incumbent Directors
either actually (because they were directors at the beginning of such 24-month
period) or by prior operation of this Paragraph (ii); or

    (iii) The occurrence of a transaction requiring stockholder approval for
the acquisition of the Company by an entity other than the Company or a
subsidiary through purchase of assets, or by merger, or otherwise.


<PAGE>   4



                                     INTEROFFICE COMMUNICATION

[AETNA LOGO]

                                     JAMES H. GOULD
                                     Vice President
                                     Compensation, Benefits & HR Services, RW2A
                                     (860) 273-8588
                                     Fax:  (860) 273-2030

To:           Thomas J. McInerney

Date:         June 26, 2000

Subject:      Change in Control Excise Tax Policy for Selected Officers

Pursuant to the memorandum agreement (the "Agreement") provided to you by Aetna
Inc. (together with any successor, "Aetna") as of the date hereof setting forth
your severance protection in the event of a change in control, you have agreed
that you will be subject to the Aetna Change in Control Excise Tax Policy for
Selected Officers. This memorandum sets forth the terms of that policy as it
applies to you.

1.   Initial Determinations by Accounting Firm.
     ------------------------------------------
     In the event that a change in "the ownership or effective control" of
     Aetna or "the ownership of a substantial portion of the assets" of Aetna
     (a "Change in Ownership") occurs or is expected to occur (in either case
     within the meaning of Section 280G of the Internal Revenue Code of 1986,
     as amended (the "Code")), Aetna shall retain a national accounting firm
     selected by Aetna and reasonably acceptable to you (the "Accounting Firm")
     to perform the calculations necessary under this memorandum. The
     Accounting Firm shall have discretion to retain an independent appraiser
     with adequate expertise (the "Appraiser") to provide any valuations
     necessary for the Accounting Firm's calculations hereunder. Aetna shall
     pay all the fees and costs associated with the work performed by the
     Accounting Firm and any Appraiser retained by the Accounting Firm. If the
     Accounting Firm has performed services for any person, entity or group in
     connection with the Change in Ownership, you may select an alternative
     national accounting firm to be the Accounting Firm. If the Appraiser
     otherwise performs work for any of the entities involved in the Change in
     Ownership or their affiliates (or has performed work for any such entity
     within the three years preceding the calculations hereunder), then you may
     select an alternative appraiser of national stature with adequate
     expertise to be the Appraiser. The Accounting Firm shall provide promptly
     to both Aetna and you a written report setting forth the calculations
     required under this memorandum, together with a detail of all relevant
     supportive data, valuations and calculations. All determinations of the
     Accounting Firm shall be binding on you and Aetna. When making the
     calculations required hereunder, you shall be deemed to pay:

     -   Federal income taxes at the highest applicable marginal rate of
         Federal income taxation for the taxable year for which any such
         calculation is made, and

     -   any applicable state and local income taxes at the highest applicable
         marginal rate of taxation for the taxable year for which any such
         calculation is made, net of the maximum reduction in Federal income
         taxes which could be obtained from deduction of such state and local
         taxes.

<PAGE>   5

     The Accounting Firm shall determine (the "Initial Determination"):

     (i) the aggregate amount of all payments, benefits and distributions
         provided by Aetna to you or for your benefit, whether paid or payable
         or distributed or distributable pursuant to the terms of the Agreement
         or any other agreement, plan or arrangement of Aetna or otherwise
         (other than any payment pursuant to this memorandum) which are in the
         nature of compensation and contingent upon a Change in Ownership
         (valued pursuant to Section 280G of the Code) (collectively the
         "Payments"); and

     (ii)the maximum amount of the Payments you would be entitled to receive
         without being subject to the excise tax imposed by Section 4999 of the
         Code (the "Payment Cap") (such excise tax, together with any interest
         or penalties with respect to such excise tax, are hereinafter
         collectively referred to as the "Excise Tax").

2.   Initial Treatment of Payments.
     ------------------------------
     (a) If the amount of the Payments does not exceed the Payment Cap, you
         shall be entitled to receive the full amount of the Payments.

     (b) If the amount of the Payments exceeds the Payment Cap by less than 10%
         of the Payment Cap amount, then, notwithstanding anything to the
         contrary, the amount of the Payments payable to you shall be reduced
         to the amount of the Payment Cap. In the event that the Payments are
         subject to reduction hereunder, you shall have the right to designate
         which of the Payments will be reduced or eliminated.

     (c) If the amount of the Payments exceeds the Payment Cap by more than 10%
         of the Payment Cap amount, then the amount of the Payments you are
         entitled to receive shall not be reduced and Aetna shall pay to you an
         additional payment (a "Gross-Up Payment") in an amount such that after
         payment by you of all taxes (including any interest and penalties
         imposed with respect to such taxes), including any Excise Tax, imposed
         upon the Gross-Up Payment you retain an amount of the Gross-Up Payment
         equal to the Excise Tax imposed upon the Payments. All determinations
         required to be made as to whether a Gross-Up Payment is required and
         the amount of such Gross-Up Payment shall be made by the Accounting
         Firm.

3.   Redeterminations Based on IRS or Court Ruling.
     ----------------------------------------------
     If after the date of the Initial Determination (A) you become entitled to
     receive additional Payments (including, without limitation, severance)
     contingent upon the same Change in Ownership, or (B) you become subject to
     the terms of any final binding agreement between you and the Internal
     Revenue Service or any decision of a court of competent jurisdiction which
     is not appealable or for which the time to appeal has lapsed (a "Final
     Determination") and which is contrary to the Initial Determination, then
     based upon such additional Payments or such Final Determination (as the
     case may be), the Accounting Firm shall recalculate:

     (i) the aggregate Payments (such recalculated amount, the "Redetermined
         Payments"); and

                                       2

<PAGE>   6

     (ii) the maximum amount of the Redetermined Payments you would be entitled
          to receive without being subject to the excise tax imposed by Section
          4999 of the Code (the "Redetermined Payment Cap") (such excise tax,
          together with any interest or penalties with respect to such excise
          tax, are hereinafter referred to as the "Redetermined Excise Tax").

4.   Reconciliations Based on Redeterminations.
     ------------------------------------------
     (a) If the Redetermined Payment Cap is greater than the Payment Cap (and
         your Payments were reduced pursuant to paragraph 2(b)), then Aetna
         shall promptly pay you the amount by which the Redetermined Payments
         Cap exceeds the Payment Cap, together with interest on such difference
         at the applicable Federal rate (as defined in Section 1274(d) of the
         Code) (the "Federal Rate") from the original Payment due date to the
         date of actual payment of the difference by Aetna.

     (b) If the aggregate value of the Redetermined Payments exceeds the
         Redetermined Payment Cap by less than 10%, then, notwithstanding
         anything to the contrary, the amount of the Redetermined Payments that
         you are entitled to receive and retain shall be reduced to the amount
         of the Redetermined Payment Cap. In the event that the Redetermined
         Payments are subject to reduction under this paragraph and any such
         portion of the Redetermined Payments have not yet been paid to you, you
         shall have the right to designate which portion of such unpaid
         Redetermined Payments should be reduced or eliminated. If you have
         previously received any Payments in excess of the Redetermined Payment
         Cap, such excess Payments shall be deemed for all purposes to be a
         loan to you made on the date of receipt of such excess Payments, which
         you shall have an obligation to repay to Aetna on demand, together
         with interest on such amount at the applicable Federal rate (as
         defined in Section 1274(d) of the Code) from the date of your receipt
         of such excess Payments to the date of repayment by you.
         Notwithstanding the foregoing, if any portion of such excess Payments
         which is to be refunded to Aetna has been paid to any Federal, state
         or local tax authority, repayment thereof shall not be required until
         actual refund or credit of such portion has been made to you, and
         interest payable to Aetna shall not exceed interest received or
         credited to you by such tax authority for the period it held such
         portion. In addition, if, pursuant to a Final Determination, any such
         excess Payments are not deemed a loan and as a result you are subject
         to Redetermined Excise Tax, then you shall be treated as if the
         aggregate value of the Redetermined Payments exceeds the Redetermined
         Payment Cap by more than 10% under paragraph 3(c) and you shall be
         entitled to the Supplemental Gross-Up Payment, subject to all the
         attendant conditions set forth below.

     (c) If the aggregate value of the Redetermined Payments exceeds the
         Redetermined Payment Cap by more than 10%, then the amount of the
         Redetermined Payments you are entitled to receive and retain shall not
         be reduced and Aetna shall pay to you an additional payment (a
         "Supplemental Gross-Up Payment") in an amount such that after payment
         by you of all taxes (including any interest and penalties imposed with
         respect to such taxes), including any Redetermined Excise Tax, imposed
         on the Supplemental Gross-Up Payment you retain an amount of the
         Supplemental Gross-Up Payment; provided that if you have previously
         received a Gross-Up Payment, the amount of the Supplemental Gross-Up
         Payment shall be reduced by the amount of the Gross-Up Payment you
         previously received, so that you will be

                                       3

<PAGE>   7

         fully reimbursed, but will not receive duplicative reimbursements. If,
         however, the Excise Tax exceeds the Redetermined Excise Tax, the
         excess Gross-Up Payment that has been paid to you shall be deemed for
         all purposes to be a loan to you made on the date of receipt of such
         excess Gross-Up Payment, which you shall have an obligation to repay
         to Aetna on demand, together with interest on such amount at the
         applicable Federal rate (as defined in Section 1274(d) of the Code)
         from the date of your receipt of such excess Gross-Up Payment to the
         date of repayment by you. Notwithstanding the foregoing, in the event
         any portion of the Gross-Up Payment to be refunded to Aetna has been
         paid to any Federal, state or local tax authority, repayment thereof
         shall not be required until actual refund or credit of such portion
         has been made to you, and interest payable to Aetna shall not exceed
         interest received or credited to you by such tax authority for the
         period it held such portion. You and Aetna shall mutually agree upon
         the course of action to be pursued (and the method of allocating the
         expenses thereof) if your good faith claim for refund or credit is
         denied.

5.   Procedures With Respect to IRS Claims.

     You shall notify Aetna in writing of any claim by the Internal Revenue
     Service relating to any unpaid excise tax applicable to the Payments. Such
     notification shall be given as soon as practicable but no later than
     twenty business days after you know of such claim and shall apprise Aetna
     of the nature of such claim, any assessment under such claim and the date
     on which such assessment is requested to be paid. You shall not pay such
     claim prior to the expiration of the thirty day period following the date
     on which you give such notice to Aetna (or such shorter period ending on
     the date that any payment of taxes with respect to such claim is due). If
     Aetna notifies you in writing prior to the expiration of such period that
     it desires to contest such claim, you shall:

     (a) give Aetna any information reasonably requested by Aetna relating to
         such claim,

     (b) take such action in connection with contesting such claim as Aetna
         shall reasonably request in writing from time to time including,
         without limitation, accepting legal representation with respect to
         such claim by an attorney reasonably selected by Aetna,

     (c) cooperate with Aetna in good faith in order to effectively contest
         such claim, and

     (d) permit Aetna to participate in any proceedings relating to such claim;

     provided, however, that Aetna shall bear and pay directly all costs and
     expenses (including additional interest and penalties) incurred in
     connection with such contest and shall indemnify and hold you harmless, on
     an after-tax basis, for any Excise Tax, Redetermined Excise Tax or income
     tax, including interest and penalties with respect thereto, imposed as a
     result of such representation and payment of costs and expenses. Without
     limitation on the foregoing, Aetna shall control all proceedings taken in
     connection with such contest and, at its sole option, may pursue or forego
     any and all administrative appeals, proceedings, hearings and conferences
     with the taxing authority in respect of such claim and may, at its sole
     option, either direct you to pay the tax claimed and sue for a refund or
     contest the claim in any permissible manner, and you agree to prosecute
     such contest to a determination before any administrative tribunal, in a
     court

                                       4

<PAGE>   8

     of initial jurisdiction and in one or more appellate courts, as Aetna
     shall determine; provided, however, that if Aetna directs you to pay such
     claim and sue for a refund, Aetna shall advance the amount of such payment
     to you, on an interest-free basis, and shall indemnify and hold you
     harmless, on an after-tax basis, from any Excise Tax, Redetermined Excise
     Tax or income tax, including interest and penalties with respect thereto,
     imposed with respect to such advance or with respect to any imputed income
     with respect to such advance; and further provided that any extension of
     the statute of limitations relating to payment of taxes for the taxable
     year of you with respect to which such contested amount is claimed to be
     due is limited solely to such contested amount. Furthermore, Aetna's
     control of the contest shall be limited to issues with respect to which a
     Gross-Up Payment would be payable hereunder and you shall be entitled to
     settle or contest, as the case may be, any other issue raised by the
     Internal Revenue Service or any other taxing authority.

     If after the receipt by you of an amount advanced by Aetna pursuant to the
     foregoing, you become entitled to receive any refund with respect to such
     claim, you shall (subject to Aetna's complying with the requirements of
     above with respect to any contestation of an excise tax claim) promptly
     pay to Aetna the amount of such refund (together with any interest paid or
     credited thereon by the taxing authority after deducting any taxes
     applicable thereto). If, after the receipt by you of an amount advanced by
     Aetna hereunder, a determination is made that you shall not be entitled to
     any refund with respect to such claim and Aetna does not notify you in
     writing of its intent to contest such denial of refund prior to the
     expiration of thirty days after such determination, then such advance
     shall be forgiven and shall not be required to be repaid and the amount of
     such advance shall offset, to the extent thereof, the amount of the
     Supplemental Gross-Up Payment required to be paid hereunder. The
     forgiveness of such advance shall be considered part of the Supplemental
     Gross-Up Payment and subject to gross-up for any taxes (including interest
     or penalties) associated therewith.

     The terms of this document shall not be amended, modified or curtailed
     without your written consent.

                                       5