<PAGE>

Exhibit 10.25

July 8, 1999


Bob Barbiere
Vice President
Arbinet
226 E. 54th Street
New York, New York  10022

Re: IT Assessment

Dear Bob:

Thank you for selecting Breakaway, as a provider of business and technology
services to your company. Breakaway, provides quality services using
professional methods, procedures and personnel to help you and your company
accomplish your business objectives in a timely manner.

In order to begin this relationship between Arbinet and Breakaway, we recognize
the importance of having a clear definition of the goals and objectives of this
engagement. A successful relationship requires active and informed involvement
on the part of both organizations. Clearly defined ground rules reduce
misunderstandings that could impact the expected results and help maintain an
optimum delivery environment.

The following represents the consulting agreement and understanding between
Breakaway and Arbinet:

1.       UNDERSTANDING AND SCOPE OF SERVICES

The scope of this project is to:

         1.       Assess the current state of Arbinet online exchange
                  initiative.

         2.       Provide the recommended solution as required.

The design of the IT Assessment is the following:

          Balances business and technical perspectives
          Evolved from architectural and organizational research funded by DARPA
          Leverages Breakaway's insight and experiences into the venture space
<PAGE>

         Packages consulting services into fixed price, tangible deliverable (8
         to 10 page report)
         Productize service to maximize the value, minimize the costs, and
         ensure quality
         Focus on rapid turn around to support deal cycle

The approach for the IT assessment is the following:

         Review Business Plan
         Construct detail Evaluation Workbook prior to visit based upon
         industry, enabling technologies, and business plan review
         One day visit to venture's facility
         Conduct 1 hr structured interviews with a cross-section of the
         venture's management & technical team: CEO, VP Marketing, VP of
         Technology, and 2-3 developers
         Post-visit research on key issues and competitors
         Development of 8 to 10 page report by 7/19/99

The deliverable (report) format is the following:

         Introduction
         Findings
         People
         Business Model
         Enabling Technology
         Competitive Forces
         Evaluation Steps

The overall benefits of this approach constitutes the following:

         Proven approach that has been used on more than 30 engagements
         Senior evaluators who have thrived in both the Fortune 500 and start-up
         worlds
         Objective and detailed review of business model and enabling technology
         Frank assessment of management teams' experience and capacity
         Identification of competitive forces
         Rapid turn around with minimal impact on venture
         Detailed/Actionable 8-10 page report


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<PAGE>

2.       ASSUMPTIONS

The following assumptions have been made in setting the pricing specified above.
Any deviation from these assumptions may increase the cost of the project.

         The named resources from Arbinet must be available on a full time basis
         during the one day IT Assessment session (i.e., Bob Barbiere, Tony
         Craig, and members of the technical staff).
         Breakaway must have access to the business plan prior to the beginning
         of the assessment period.

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
ARBINET RESOURCE          PREP (DAYS)      IT ASSESSMENT           ASSESSMENT
                                           SESSION (DAYS)          REVIEW (DAYS)
--------------------------------------------------------------------------------
<S>                       <C>              <C>                     <C>
Bob Barbiere, VP          0.25             1                       0.25
--------------------------------------------------------------------------------
Tony Craig, CEO           0                1                       0.25
--------------------------------------------------------------------------------
Ken Amron, VP
Development
--------------------------------------------------------------------------------
Alex Mashinsky
Founder, Acting CTO
--------------------------------------------------------------------------------
</TABLE>

NOTE: THE TIME NECESSARY FOR THESE RESOURCES MAY INCREASE AND/OR DECREASE
DEPENDING ON THE LEVEL OF SPECIFICITY REQUIRED BY THE CLIENT TEAM. WE ANTICIPATE
THAT EACH FULL DAY OF CLIENT TEAM EFFORT WILL CONSTITUTE 6 HOURS/DAY.

3.       TIME FRAME

We will make every effort to begin this project as soon as possible, after
contract signing. Projects can generally begin, 2 weeks from receiving a signed
agreement based on staffing requirements. We will work with you to reach an
agreeable time frame. Our resource availability is highly dependent upon when
the services contract is signed by our client. We have schedule d a July 15th
date for this initiative.

Upon completion of the IT Assessment process Breakaway will assume that the
client (Arbinet) will proceed with the 360 Workshop and the development phase of
the project lifecycle.


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<PAGE>

The first stage of our development process is termed an AIM (Accelerated
Implementation Model).

4.       RESOURCES

Breakaway will provide resources for the project to be assigned on an as needed
basis. Project resources are described below:

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
        BREAKAWAY RESOURCE           PREP      SITE VISIT       DELIVERABLE
                                    (DAYS)    SESSION (DAYS)    PREPARATION
                                                                 & REVIEW
--------------------------------------------------------------------------------
<S>                                  <C>          <C>              <C>
Internet Solutions VP                  0            1                .5
--------------------------------------------------------------------------------
Internet Solutions Managing            0            1               1.5
Director
--------------------------------------------------------------------------------
Senior Consultant                      1            1               1
--------------------------------------------------------------------------------
</TABLE>

5.       COST AND PAYMENT TERMS

Professional service fees stated below constitute a fixed price bid.

The fixed price bid is INCLUSIVE of out-of-pocket expenses. Out-of-pocket
expenses will include and not be limited to travel, hotel and meal per diems. In
building a business partnership with Arbinet, Breakaway is confident that this
will be a long-term and mutually beneficial one, and so expense payment is
waived at this time.

Professional service fees for the IT Assessment is listed below. We require a
50% deposit prior to beginning work. This bid is effective through July 14, 1999
and is subject to change.

ARBINET DISCOUNTED COST:

<TABLE>
<CAPTION>
---------------------------------------
  PROJECT PHASE             FIXED PRICE
---------------------------------------
<S>                          <C>
ITT Assessment               $10,000
---------------------------------------
Total                        $10,000
---------------------------------------
</TABLE>


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<PAGE>

The contents of the attached Standard Terms and Conditions of Breakaway are
hereby incorporated by reference, as fully stated herein.

We look forward to the opportunity to provide these services to you. Should you
have any questions, please call me at your convenience.

Very truly yours,


Thomas D. Berger
Regional Account Manager
Breakaway Solutions


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<PAGE>

AGREEMENT

By evidence of their signature below, both parties agree to the terms and
conditions as set forth in this Engagement Letter.


Arbinet                              Breakaway Solutions, Inc.

By: /s/ Robert Barbierie             By:
   -------------------------            -------------------------

Title:  VP Bus & Mrkt. Dev.          Title:
      ----------------------               ----------------------

Date: 7/11/99                        Date:
     -----------------------              -----------------------


STANDARD TERMS AND CONDITIONS

Professional Fees & Expenses

Except for work within the scope of a fixed price engagement, we determine our
fees by actual time spent, based upon our standard rates, as stated in an
Engagement Letter. Our standard workday is normally 10 hours, but there are no
additional charges or fee premiums for "over-time." If during the course of the
engagement, we determine circumstances are such that substantially greater work
is required than is estimated we will not move forward without prior written
approval.

Reasonable out-of-pocket expenses are billed in addition to consulting time.
Out-of-pocket expenses are not normally included in estimates, but remain the
responsibility of the client.

DEPOSIT AND PAYMENT TERMS

Unless otherwise specified in an Engagement Letter, a deposit on account of 50%
of the Engagement Letter's _____ is payable upon execution of the Engagement
Letter. The deposit will be applied against the open balance at the conclusion
of the project. Invoices will be sent semi-monthly, and all invoices are payable
upon receipt.


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<PAGE>

INTELLECTUAL PROPERTY RIGHTS

In the course of the consulting engagement, Breakaway Solutions Inc., may use
enhancements, discoveries, processes, methods, designs and know-how, whether or
not they may be copyrighted or patented, which Breakaway Solutions Inc.
conceived during the course of other consulting engagements. In addition,
Breakaway Solutions Inc. may independently develop enhancements, processes,
methods, designs or know-how during the term of this consulting engagement and
The Client acknowledges that Breakaway Solutions Inc. may use such enhancements,
processes, methods, designs and know-how in its business operations with other
clients.

LIMITATION LIABILITY

The entire liability of Breakaway Solutions Inc. to The Client, or any other
party for any loss or damage resulting from any claims, demands or actions
arising out of an Engagement Letter or the performance of or failure to perform
specific consulting services shall not exceed the fees paid to Breakaway
Solutions Inc. for the software and services rendered, except in the case of
gross negligence or intentional misconduct on the part of The Counsel Group, in
which case Breakaway Solutions Inc. will bear the cost of remedying the damage
caused by its gross negligence or intentional misconduct within 30 days of the
occurrence.

In no event will Breakaway Solutions Inc. be liable for any indirect,
incidental, consequential, special or exemplary damages whatsoever (including
without limitation damages for loss of business profits, business interruption,
loss of business information, or other pecuniary loss) arising out of this
Engagement Letter for the performance of specific consulting services or for
acts of negligence that are not reckless or intentional in nature, even if the
party has been advised of the possibility of such damages.

CONFIDENTIALITY

During the course of performing services, Breakaway Solutions Inc. and The
Client may have access to information that is confidential to one another
("Confidential Information"), including without limitation, source code,
documentation, specifications, data bases, system design, file layouts, tool
combinations, development methods. Confidential Information also includes
business or financial affairs, which may incorporate business methods, marketing
strategies, pricing, competitor information, product development strategies and
methods, costumer lists and financial results. Confidential Information also
includes information received from others, both written and oral, that each
party is obligated to treat as confidential. Confidential Information shall


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<PAGE>

not include any information that (1) is already known by the recipient party or
its affiliates, free of any obligation to keep it confidential, (2) is or
becomes publicly known through no wrongful act of the receiving party or its
affiliates, (3) is received by the receiving party from a third party without
any restriction on confidentiality, (4) is independently developed by the
receiving party or its affiliates, (5) is disclosed to third parties by the
disclosing party without any obligation of confidentiality, or (6) is approved
for release by prior written authorization of the disclosing party.

The parties agree to maintain the confidentiality of the Confidential
Information and to protect as a trade secret any portion of the other party's
Confidential Information by preventing any unauthorized copying, use,
distribution, installation or transfer of possession of such information. Each
party agrees to maintain at least the same procedures regarding Confidential
Information that it maintains with respect to its own Confidential Information.
Each party may use the Confidential Information received from the other party
only in connection with fulfilling its obligations under a consulting
engagement.

INDEPENDENT CONTRACTOR

Breakaway Solutions Inc. is an independent contractor. Neither Breakaway
Solutions Inc. nor The Client are, or shall be deemed for any purpose to be,
employees or agents of the other and neither party shall have the power or
authority to bind the other party to any contract or obligation. Breakaway
Solutions Inc. shall retain the right to perform work for others during the term
of a consulting engagement.

REGARDING BREAKAWAY SOLUTIONS INC. EMPLOYEES

Whereas Breakaway Solutions Inc. regards its employees as valuable assets, it is
expected that The Client will in no way solicit for hire or for consulting
services outside of a consulting engagement with Breakaway Solutions Inc.
without written authorization from the President of Breakaway Solutions Inc. for
a period of at least one year following termination of such employee from
Breakaway Solutions Inc. If authorization is given to client to hire any
Breakaway Solutions Inc. employee, it is expected that satisfactory compensation
will be given to Breakaway Solutions Inc. for such privilege, which will be
agreed upon by both parties.


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<PAGE>

INSURANCE

Breakaway Solutions Inc. warrants that it maintains all normal business
insurance required for a Delaware corporation doing business in the Commonwealth
of Massachusetts.

WARRANTIES

Breakaway Solutions Inc. warrants that it has full power and authority to enter
into a Consulting Engagement with The Client. Breakaway Solutions Inc. warrants
that all services will be performed consistent with generally accepted industry
standards and in a workmanlike manner by qualified personnel. Breakaway
Solutions Inc. disclaims all other warranties, either express or implied,
including but not limited to implied warranties of merchantability and fitness
for a particular purpose, with respect to products and services that may be
provided herein.

Third-party commercial software vendors offer warranties for software licenses
purchased by The Client. Breakaway Solutions Inc. DOES NOT warrant in any way
software manufactured by any third-party.

TERMINATION

Either party may terminate services performed under this agreement with 10 days
notice to the other party without cause, or immediately with reasonable cause.
Work not performed to the reasonable satisfaction of The Client, or failure
reasonably to pay invoices for services rendered shall be considered reasonable
cause. Upon termination for any reason, Breakaway Solutions Inc. shall be paid
all hourly fees earned to the point of termination.

Arbitration and Litigation

Any controversy or claim arising out of or relating to this Agreement or the
breach thereof will be settled by arbitration by a single arbitrator in
accordance with the Commercial Arbitration Rules of the American Arbitration
Association (AAA) then in effect, and judgment upon the award rendered by the
arbitrator may be entered in any court having jurisdiction. Any such arbitration
will be conducted in or near Boston, Massachusetts. The prevailing party shall
be entitled to receive from the other party its attorney's fees and costs
incurred in connection with any action, proceeding or arbitration hereunder.


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<PAGE>

Either party, before or during any arbitration, may apply to a court having
jurisdiction for a temporary restraining order or preliminary injunction, where
such relief is necessary to protect its interest pending completion of the
arbitration proceedings.

GOVERNING LAW

This Agreement shall be governed by and construed in accordance with the laws of
the Commonwealth of Massachusetts.

SEVERABILITY

In the event any one or more of the provisions of this Agreement is held to be
invalid or otherwise unenforceable, the enforceability of the remaining
provisions shall be unimpaired.

ASSIGNMENT

This Agreement, and any right or obligation under this Agreement, may not be
assigned, transferred or delegated by either party without the express written
consent of the other party, which consent may be withheld by either party at its
sole discretion.

FORCE MAJEURE

Breakaway Solutions Inc. shall not be responsible for failure to perform in a
timely manner under a Consulting Engagement when its failure results from any of
the following causes: acts of God or public enemies, civil war, insurrection or
riot, fire, flood, explosion, earthquake or serious accident, strike, labor
trouble or work interruption or any cause beyond its reasonable control.

ENTIRE AGREEMENT

In conjunction with a fully executed Engagement Letter, these Terms & Conditions
constitutes the entire Agreement between the parties. Each party agrees that the
Engagement Letter and Terms & Conditions are the complete and exclusive
statement of the parties regarding the specific subject matter hereof and
supersedes and merges all prior proposals, understandings and agreements, oral
or written, between the parties


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<PAGE>

relating to the subject matter hereof, including without limitation, the terms
of any request for proposal issued to The Client or the standard printed terms
on any purchase order issued by The Client. No modification, amendment,
supplements to or waiver of this Agreement shall be binding upon the parties
unless made in writing and duly signed by both parties.


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