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                                                                   EXHIBIT 10.18

                           [UNICA COMPANY LETTERHEAD]


August 30, 2005

Chanchal Samanta
6 Palmer Lane
Acton MA 01720

Dear Chanchal:

This letter will confirm the agreement that we have reached regarding your
separation from employment. The purpose of this Agreement is to establish an
amicable arrangement for ending your employment relationship, to release Unica
("Unica" or "Company") from any claims and to permit you to receive fair and
reasonable separation pay and related benefits.

This is an agreement you are entering into voluntarily. It is customary in
employment separation agreements for the departing employee to release the
employer from any possible claim, even if the employer believes, as is the case
here, that no such claims exist. You understand that you are giving up your
right to bring any and all possible legal claims against Unica. Neither the
Company nor you want your employment relationship to end with a legal dispute.
By entering into this agreement, you understand that Unica is not admitting in
any way that it violated any legal obligation that it owed to you. To the
contrary, Unica's willingness to enter into this agreement demonstrates that it
is continuing to deal with you fairly and in good faith.

With that understanding, you and Unica agree as follows:

      1.    Employment Termination Date. Your employment with Unica is
            terminated as of February 28, 2006.
            a.    As of the Termination Date, your salary will cease, and any
                  entitlement you have or might have under a Company-provided
                  benefit plan, program, contract or practice will terminate,
                  except as required by federal or state law, or as otherwise
                  described below.
            b.    On the Termination Date, you will be paid all wages earned but
                  unpaid and all accrued but unused vacation time up to and
                  through the Termination Date.
            c.    The Termination Date shall be the date of the "qualifying
                  event" under the Consolidated Omnibus Budget Reconciliation
                  Act of 1985 ("COBRA") and the Company will present you with
                  information on COBRA under separate cover.

      2. Resignation and Transition Support. Effective September 20, 2005, you
resign from your current position as Vice President of Development and will
assume the title of Senior Consultant reporting to John Hogan. During the period
September 20, 2005 through December 31, 2005, you will provide transition
support as requested by John Hogan which may include areas such as providing
historic performance documentation for development employees, including
assistance in the performance review process, as well as special projects
requested by John Hogan.

      3. Base Salary, Bonus, and Benefits. From September 20, 2005, through
December 31, 2005, you will continue to receive your current base salary. You
are also eligible to receive your target bonus for the fourth quarter of fiscal
2005. Your fourth quarter bonus will be determined in the same manner as other
participants in the Executive Bonus Plan. You will receive full benefits through
your February 28, 2006 termination date.

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      4. Stock Options. You will continue to vest in the Company's 2005 Stock
Option Plan through your termination date.

      5. Release of Claims. In consideration of the payments and benefits
described in paragraphs 2, 3, and 4 to which you acknowledge you would not
otherwise be entitled, you voluntarily release and forever discharge Unica, its
affiliates, subsidiaries, successors and assigns, and their current and former
officers, directors, employees, attorneys, accountants and agents, in their
official and personal capacities (collectively referred to as the "Releasees"),
generally from all claims, demands, debts, damages and liabilities of every name
and nature, known or unknown, which exist or have existed up to and including
the date you sign this letter, including but not limited to claims relating to
your employment by and termination from the Company, including but not limited
to wrongful discharge claims; breach of contract claims; state and federal
discrimination claims (including without limitation claims of age discrimination
under the Age Discrimination in Employment Act and any claims concerning sex,
sexual orientation or sexual harassment), defamation and other tort claims;
statutory claims; claims for wages, bonuses, incentive compensation, vacation
pay or any other compensation or benefits; and claims for compensatory damages,
punitive damages and attorneys fees.

      6. Confidentiality of this Agreement. You agree to keep the existence and
terms of this agreement in the strictest confidence and not reveal, unless
legally compelled to do so, the terms of this agreement to any person except
your spouse, your attorney and your financial advisors, provided that they also
agree to keep the information confidential.

      7. Company Files, Documents, and Other Property. You agree that on or
before the Termination Date you will return to the Company all Company property
and materials, including but not limited to, (if applicable) personal computers,
laptops, fax machines, scanners, copiers, cellular phones, Company credit cards
and telephone charge cards, manuals, building keys and passes, courtesy parking
passes, diskettes, intangible information stored on diskettes, software programs
and data compiled with the use of those programs, software passwords or codes,
tangible copies of trade secrets and confidential information, sales forecasts,
names and addresses of Company customers and potential customers, customer
lists, customer contacts, sales information, sales forecasts, memoranda, sales
brochures, business or marketing plans, reports, projections, and any and all
other information or property previously or currently held or used by you that
is or was related to your employment with the Company ("Company Property"). You
agree that in the event that you discover any other Company Property in your
possession after the Termination Date of this Agreement you will immediately
return such materials to the Company.

      8. Nondisparagement. You agree not to make disparaging, critical or
otherwise detrimental comments to any person or entity concerning the Company,
its officers, directors or employees; the products, services or programs
provided or to be provided by the Company; the business affairs, operation,
management or the financial condition of the Company; or the circumstances
surrounding your employment and/or separation of employment from the Company.

      9. Legal Representation. This agreement is a legally binding document and
your signature will commit you to its terms. You acknowledge that you have been
advised by Unica to discuss all aspects of this agreement with your attorney
before signing it, that you have carefully read and fully understand all of the
provisions of this agreement and that you are knowingly and voluntarily entering
into this agreement.

      10. Other Provisions. You will have forty-five (45) days to consider
whether to accept the terms of this agreement. If you sign this agreement within
less than forty-five (45) days of the date of its delivery to you, you
acknowledge that such decision was entirely voluntary and that you had the
opportunity to consider this agreement for the entire forty-five (45) day
period. For a period of seven (7) days following your execution of this
agreement, you may revoke it by written notice delivered to the undersigned.
This agreement shall not become effective or enforceable until the seven (7) day
revocation period has expired.

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      11. Reference. Unica will provide you with a job reference regarding your
employment at the Company upon your request.


      12. Non-Competition, Nondisclosure, and Developments Agreement. You
reaffirm the provisions of the Non-competition, Nondisclosure, and Developments
agreement you signed on January 25, 2002, and agree to abide by all of its
terms. The foregoing sentence is an integral part of Unica's agreement to enter
into this letter.

      13. Miscellaneous. This letter constitutes the entire agreement regarding
your separation from employment with Unica, and supersedes any previous
agreements or understandings between us. If any provision of this Agreement, or
part thereof, is held invalid, void or voidable as against public policy or
otherwise, the invalidity shall not affect other provisions, or parts thereof,
which may be given effect without the invalid provision or part.

This agreement will be interpreted and enforced under the laws of the
Commonwealth of Massachusetts, without regard to conflict of law principles. You
may not assign any of your rights or delegate any of your duties under this
agreement. The rights and obligations of the Company shall inure to the benefit
of the Company's successors and assigns.

Please indicate your agreement to the terms of this Agreement by signing and
returning to me a copy of this letter by October 14, 2005.

Once again, I want to thank you for your contributions to Unica and wish you the
best in your future endeavors.

Sincerely,

/s/ Yuchun Lee

Yuchun Lee
Chief Executive Officer

I REPRESENT THAT I HAVE READ THE FOREGOING AGREEMENT, THAT I FULLY UNDERSTAND
THE TERMS AND CONDITIONS OF SUCH AGREEMENT AND THAT I AM KNOWINGLY AND
VOLUNTARILY EXECUTING THE SAME. IN ENTERING INTO THIS AGREEMENT, I DO NOT RELY
ON ANY REPRESENTATION, PROMISE OR INDUCEMENT MADE BY THE COMPANY OR ITS
REPRESENTATIVES WITH THE EXCEPTION OF THE CONSIDERATION DESCRIBED IN THIS
DOCUMENT.

I understand and agree completely to the foregoing:


/s/ Chanchal Samanta                                          September 2, 2005
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Chanchal Samanta                                              Date

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                  IF YOU DO NOT WISH TO USE THE 45-DAY PERIOD,
                 PLEASE CAREFULLY REVIEW AND SIGN THIS DOCUMENT

      I, Chanchal Samanta, acknowledge that I was informed and understand that I
have 45 days within which to consider the attached Severance Agreement and
Release, have been advised of my right to consult with an attorney regarding
such Agreement and have considered carefully every provision of the Agreement,
and that after having engaged in those actions, I prefer to and have requested
that I enter into the Agreement prior to the expiration of the 45 day period.


Dated:  September 2, 2005                                  /s/ Chancal Samanta
      ------------------------------                       --------------------
                                                           Chanchal Samanta



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