<PAGE>

                                                                     EXHIBIT 4.2

     THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933.
     THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, OR HYPOTHECATED IN THE
     ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO OR AN
     OPINION OF COUNSEL (WHICH MAY BE COMPANY COUNSEL) REASONABLY SATISFACTORY
     TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES
     ACT OF 1933.

                               WARRANT AGREEMENT

                   To Purchase Shares of the Common Stock of

                          OPEN PORT TECHNOLOGY, INC.

              Dated as of August 15, 1996 (the "Effective Date")

     WHEREAS, Open Port Technology, Inc., an Illinois corporation (the
"Company") has entered into a Master Lease Agreement dated as of November 7,
1995, Equipment Schedule No. VL-2, and related Schedules (the "Leases") with
Comdisco, Inc., a Delaware corporation (the "Warrantholder"); and

     WHEREAS, the Company desires to grant to Warrantholder, in consideration
for such Leases, the right to purchase shares of its Common Stock;

     NOW, THEREFORE, in consideration of the Warrantholder executing and
delivering such Leases and in consideration of mutual covenants and agreements
contained herein, the Company and Warrantholder agree as follows:

1.   GRANT OF THE RIGHT TO PURCHASE COMMON STOCK.

     The Company hereby grants to the Warrantholder, and the Warrantholder is
entitled, upon the terms and subject to the conditions hereinafter set forth, to
subscribe to and purchase, from the Company, 21,429 fully paid and non-
assessable shares of the Company's Common Stock ("Common Stock") at a purchase
price of $1.12 per share (the "Exercise Price"). The number and purchase price
of such shares are subject to adjustment as provided for in Section 8 hereof.

     In the event the Remaining Commitment (as defined in the Leases) is
approved, then the Company hereby grants to the Warrantholder, and the
Warrantholder is entitled, upon the terms and subject to the conditions
hereinafter set forth, to subscribe to and purchase, from the Company, an
additional 92,142 shares of the Company's Common Stock at the Exercise Price
stated above.

2.   TERM OF THE WARRANT AGREEMENT.

     Except as otherwise provided for herein, the term of this Warrant
Agreement and the right to purchase Common Stock as granted herein shall
commence on the Effective Date and shall be exercisable for a period of (i)
ten (10) years or (ii) five (5) years from the effective date of the Company's
initial public offering, whichever is longer.

3.   EXERCISE OF THE PURCHASE RIGHTS.

     The purchase rights set forth in this Warrant Agreement are exercisable
by the Warrantholder in whole or in part (not to exceed four (4) different
exercises), at any time, or from time to time, prior to the expiration of the
term set forth in Section 2 above, by tendering to the Company at its
principal office a notice of exercise in the form attached hereto as Exhibit I


                                       1
<PAGE>

(the "Notice of Exercise"), duly completed and executed. Promptly upon receipt
of the Notice of Exercise and the payment of the purchase price in accordance
with the terms set forth below, and in no event later than twenty-one (21) days
thereafter, the Company shall issue to the Warrantholder a certificate for the
number of shares of Common Stock purchased and shall execute the Notice of
Exercise indicating the number of shares which remain subject to future
purchases, if any.

     The Exercise Price may be paid at the Warrantholder's election either (i)
by cash or check, or (ii) by surrender of Warrants ("Net Issuance") as
determined below. If the Warrantholder elects the Net Issuance method, the
Company will issue Common Stock in accordance with the following formula:

          X = Y(A-B)
              ------
                 A

Where:    X = the number of shares of Common Stock to be issued to the
              Warrantholder.

          Y = the number of shares of Common Stock requested to be exercised
              under this Warrant Agreement.

          A = the fair market value of one (1) share of Common Stock.

          B = the Exercise Price.

     As used herein, current fair market value of Common Stock shall mean with
 respect to each share of Common Stock:

     (i)    if the exercise is in connection with an initial public offering,
     and if the Company's Registration Statement relating to such public
     offering has been declared effective by the SEC, then the initial "Price to
     Public" specified in the final prospectus with respect to the offering;
     (the foregoing shall not be construed as giving the Warrantholder any right
     to participate in or require any such initial public offering);

     (ii)   if this warrant is exercised after, and not in connection with the
     Company's initial public offering, and:

          (a) if traded on a securities exchange, the fair market value shall be
          deemed to be the average of the closing prices over a twenty-one (21)
          day period ending three days before the day the current fair market
          value of the securities is being determined; or

          (b) if actively traded over-the-counter, the fair market value shall
          be deemed to be the average of the closing bid and asked prices quoted
          on the NASDAQ system (or similar system) over the twenty-one (21) day
          period ending three days before the day the current fair market value
          of the securities is being determined;

     (iii)  if at any time the Common Stock is not listed on any securities
     exchange or quoted in the NASDAQ System or the over-the-counter market, the
     current fair market value of Common Stock shall be the highest price per
     share which the company could obtain from a willing buyer (not a current
     employee or director) for shares of Common Stock sold by the Company, from
     authorized but unissued shares, as determined in good faith by its Board of
     Directors, unless the Company shall become subject to a merger, acquisition
     or other consolidation pursuant to which the


                                       2
<PAGE>

     Company is not the surviving party, in which case the fair market value of
     Common Stock shall be deemed to be the value received by the holders of the
     Company's Common Stock on a common equivalent basis pursuant to such merger
     or acquisition.

     Upon partial exercise by either cash or Net Issuance, the Company shall
promptly issue an amended Warrant Agreement representing the remaining number of
shares purchasable hereunder. All other terms and conditions of such amended
Warrant Agreement shall be identical to those contained herein, including, but
not limited to the Effective Date hereof.

4.   RESERVATION OF SHARES.

     (a)  Authorization and Reservation of Shares. During the term of this
Warrant Agreement, the Company will at all times have authorized and reserved a
sufficient number of shares of its Common Stock to provide for the exercise of
the rights to purchase Common Stock as provided for herein.

     (b)  Registration or Listing. If any shares of Common Stock required to be
reserved hereunder require registration with or approval of any governmental
authority under any Federal or State law (other than any registration under the
1933 Act, as then in effect, or any similar Federal statute then enforced, or
any state securities law, required by reason of any transfer involved in such
conversion), or listing on any domestic securities exchange, before the exercise
of this warrant, the Company will, at its expense and as expeditiously as
possible, use commercially reasonable efforts to cause such shares to be duly
registered, listed or approved for listing on such domestic securities exchange,
as the case may be.

5.   NO FRACTIONAL SHARES OR SCRIP.

     No fractional shares or scrip representing fractional shares shall be
issued upon the exercise of the Warrant, but in lieu of such fractional shares
the Company shall make a cash payment therefor upon the basis of the Exercise
Price then in effect.

6.   NO RIGHTS AS SHAREHOLDER.

     This Warrant Agreement does not entitle the Warrantholder to any voting
rights or other rights as a shareholder of the Company prior to the exercise of
the Warrant.

7.   WARRANTHOLDER REGISTRY.

     The Company shall maintain a registry showing the name and address of the
registered holder of this Warrant Agreement.

8.   ADJUSTMENT RIGHTS.

     The purchase price per share and the number of shares of Common Stock
purchasable hereunder are subject to adjustment, as follows:

     (a)  Merger and Sale of Assets. If at any time there shall be a capital
reorganization of the shares of the Company's stock (other than a combination,
reclassification, exchange or subdivision of shares otherwise provided for
herein), or a merger or consolidation of the Company with or into another
corporation when the Company is not the surviving corporation, or the sale of
all or substantially all of the Company's properties and assets to any other
person (hereinafter referred to as a "Merger Event"), then, as a part of such
Merger Event, lawful provision shall be made so that the Warrantholder shall


                                       3

<PAGE>

thereafter be entitled to receive, upon exercise of the Warrant, the number of
shares of Common stock or other securities of the successor corporation
resulting from such Merger Event, equivalent in value to that which would have
been issuable if Warrantholder had exercised this warrant immediately prior to
the Merger Event. In any such case, appropriate adjustment (as determined in
good faith by the Company's Board of Directors) shall be made in the application
of the provisions of this Warrant Agreement with respect to the rights and
interest of the Warrantholder after the Merger Event to the end that the
provisions of this Warrant Agreement (including adjustments of the Exercise
Price and number of shares of Common Stock purchasable) shall be applicable to
the greatest extent possible.

     (b)  Reclassification of Shares.  If the Company at any time shall, by
combination, reclassification, exchange or subdivision of securities or
otherwise, change any of the securities as to which purchase rights under this
Warrant Agreement exist into the same or a different number of securities of any
other class or classes, this Warrant Agreement shall thereafter represent the
right to acquire such number and kind of securities as would have been issuable
as the result of such change with respect to the securities which were subject
to the purchase rights under this Warrant Agreement immediately prior to such
combination, reclassification, exchange, subdivision or other change.

     (c)  Subdivision or Combination of Shares.  If the Company at any time
shall combine or subdivide its Common Stock, the Exercise Price shall be
proportionately decreased in the case of a subdivision, or proportionately
increased in the case of a combination.

     (d)  Stock Dividends.  If the Company at any time shall pay a dividend
payable in, or make any other distribution (except any distribution specifically
provided for in the foregoing subsections (a) or (b)) of the Company's stock,
then the Exercise Price shall be adjusted, from and after the record date of
such dividend or distribution, to that price determined by multiplying the
Exercise Price in effect immediately prior to such record date by a fraction (i)
the numerator of which shall be the total number of all shares of the Company's
stock outstanding immediately prior to such dividend or distribution, and (ii)
the denominator of which shall be the total number of all shares of the
Company's stock outstanding immediately after such dividend or distribution. The
Warrantholder shall thereafter be entitled to purchase, at the Exercise Price
resulting from such adjustment, the number of shares of Common Stock (calculated
to the nearest whole share) obtained by multiplying the Exercise Price in effect
immediately prior to such adjustment by the number of shares of Common Stock
issuable upon the exercise hereof immediately prior to such adjustment and
dividing the product thereof by the Exercise Price resulting from such
adjustment.

     (e)  Right to Purchase Additional Stock.  If, the Warrantholder's total
cost of equipment leased pursuant to the Leases exceeds $1,000,000.00,
Warrantholder shall have the right to purchase from the Company, at the Exercise
Price (adjusted as set forth herein), an additional number of shares, which
number shall be determined by (i) multiplying the amount by which the
Warrantholder's total equipment cost exceeds $1,000,000.00 by 6%, and (ii)
dividing the product thereof by the Exercise Price per share referenced above.

     (f)  Issuance of Shares at Other than Exercise Price.  If the Company
should issue shares of its Common Stock at a price per share less than the
Exercise Price in effect immediately prior to such issuance, then the Exercise
Price shall be adjusted by dividing (i) the sum of (A) the total number of
shares of the Company's Common Stock outstanding immediately prior to such
issuance multiplied by the then effective Exercise Price, and (B) the value of


                                       4
<PAGE>

the consideration received by the Company upon such issuance of such shares, by
(ii) the total number shares of the Company's Common Stock outstanding
immediately after such issuance. The Warrantholder shall thereafter be entitled
to purchase, at the Exercise Price resulting form such adjustment, the number of
shares of Common Stock (calculated to the nearest whole share) obtained by
multiplying the Exercise Price in effect immediately prior to such adjustment by
the number of shares of Common Stock issuable upon the exercise hereof
immediately prior to such adjustment and dividing the product thereof by the
Exercise Price resulting from such adjustment. For the purposes of this
paragraph (f), the issuance of securities convertible into or exercisable for
the Company's Common Stock shall be deemed the issuance of the number of shares
of the Company's Common Stock into which such securities are convertible or for
which such securities are exercisable, and the consideration received for such
securities shall be deemed to include the minimum aggregate amount payable upon
conversion or exercise of such securities. In the event the right to convert or
exercise such securities expires unexercised, the Exercise Price of shares
issuable upon the exercise hereof shall be readjusted accordingly.

     (g)  Notice of Adjustments.  If: (i) the Company shall declare any dividend
or distribution upon its stock, whether in cash, property, stock or other
securities; (ii) there shall be any Merger Event; or (iii) there shall be any
voluntary or involuntary dissolution, liquidation or winding up of the Company;
then, in connection with each such event, the Company shall send to the
Warrantholder: (A) at least twenty (20) days' prior written notice of the date
on which the books of the Company shall close or a record shall be taken for
such dividend, distribution, subscription rights (specifying the date on which
the holders of Preferred Stock shall be entitled thereto) or for determining
rights to vote in respect of such Merger Event, dissolution, liquidation or
winding up; (B) in the case of any such Merger Event, dissolution, liquidation
or winding up, at least twenty (20) days, prior written notice of the date when
the same shall take place (and specifying the date on which the holders of
Common Stock shall be entitled to exchange their Common Stock for securities or
other property deliverable upon such Merger Event, dissolution, liquidation or
winding up) . In the case of a public offering, the Company shall give the
Warrantholder at least twenty (20) days written notice prior to the effective
date thereof.

     Each such written notice shall set forth, in reasonable detail, (i) the
event requiring the adjustment, (ii) the amount of the adjustment, (iii) the
method by which such adjustment was calculated, (iv) the Exercise Price, and (v)
the number of shares subject to purchase hereunder after giving effect to such
adjustment, and shall be given by first class mail, postage prepaid, addressed
to the Warrantholder, at the address as shown on the books of the Company.

     (h)  Timely Notice.  Failure to timely provide such notice required by
subsection (g) above shall entitle Warrantholder to retain the benefit of the
applicable notice period notwithstanding anything to the contrary contained in
any insufficient notice received by Warrantholder. The notice period shall begin
on the date Warrantholder actually receives a written notice containing all the
information specified above.


9.  REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY.

     (a)  Reservation of Common Stock.  The Common Stock issuable upon exercise
of the Warrantholder's rights has been duly and validly reserved and, when
issued in accordance with the provisions of this Warrant Agreement, will be
validly issued, fully paid and non-assessable, and will be free of any taxes,
liens, charges or encumbrances of any nature whatsoever, provided,

                                       5
<PAGE>

however, that the Common Stock issuable pursuant to this Warrant Agreement may
be subject to restrictions on transfer under state and/or Federal securities
laws. The Company has made available to the Warrantholder true, correct and
complete copies of its Charter and Bylaws, as amended. The issuance of
certificates for shares of Common Stock upon exercise of the Warrant Agreement
shall be made without charge to the Warrantholder for any issuance tax in
respect thereof, or other cost incurred by the Company in connection with such
exercise and the related issuance of shares of common Stock. The Company shall
not be required to pay any tax which may be payable in respect of any transfer
involved and the issuance and delivery of any certificate in a name other than
that of the Warrantholder.

     (b)  Due Authority.  The execution and delivery by the Company of this
Warrant Agreement and the performance of all obligations of the Company
hereunder, including the issuance to Warrantholder of the right to acquire the
shares of Common Stock, have been duly authorized by all necessary corporate
action on the part of the Company, and the Leases and this Warrant Agreement are
not inconsistent with the Company's Charter or Bylaws, do not contravene any law
or governmental rule, regulation or order applicable to it, do not and will not
contravene any provision of, or constitute a default under, any indenture,
mortgage, contract or other instrument to which it is a party or by which it is
bound, and the Leases and this Warrant Agreement constitute legal, valid and
binding agreements of the Company, enforceable in accordance with their
respective terms.

     (C)  Consents and Approvals.  No consent or approval of, giving of notice
to, registration with, or taking of any other action in respect of any state,
Federal or other governmental authority or agency is required with respect to
the execution, delivery and performance by the company of its obligations under
this Warrant Agreement, except, if any, for the filing of notices pursuant to
Regulation D under the 1933 Act and Section 4(C) of the State of Illinois
Securities Act of 1953, which filings will be effective by the time required
thereby.

     (d)  Issued Securities.  All issued and outstanding shares of Common Stock,
Preferred Stock or any other securities of the Company have been duly authorized
and validly issued and are fully paid and nonassessable. All outstanding shares
of Common Stock, Preferred Stock and any other securities were issued in full
compliance with all Federal and state securities laws. In addition:

     (i) The authorized capital of the Company consists of (A) 30,000,000
shares of Common Stock, of which 12,000,000 shares are issued and outstanding,
and (B) 1,228,917 shares of Series A Convertible Participating preferred
stock, of which 1,228,917 shares are issued and outstanding and are currently
convertible into 2,457,834 shares of Common Stock at no additional
consideration, and (C) 6,026,786 shares of Series B Convertible Participating
preferred stock, the conversion value of which stock is dependent on the
Company's 1996 revenue, in accordance with a formula as stated in the articles
of incorporation.

     (ii) The Company has reserved 1,606,426 shares of Common Stock for issuance
under its stock option plans, under which 1,537,600 options as of August 20,
1996 are outstanding. There are no other options, warrants, conversion
privileges or other rights presently outstanding to purchase or otherwise
acquire any authorized but unissued shares of the Company's capital stock or
other securities of the Company.

                                       6
<PAGE>

     (iii) In accordance with the Company's Articles of Incorporation, all
preferred stockholders have preemptive rights to purchase new issuances of the
Company's capital stock.

     (e)  Insurance.  The Company has in full force and effect insurance
policies, with extended coverage, insuring the company and its property and
business against such losses and risks, and in such amounts, as are customary
for corporations engaged in a similar business and similarly situated and as
otherwise may be required pursuant to the terms of any other contract or
agreement.

     (f)  Other Commitments to Register Securities.  Except for an amended and
restated Registration Rights Agreement dated March 12, 1996 with all preferred
stockholders, the Company is not, pursuant to the terms of any other agreement
currently in existence, under any obligation to register under the 1933 Act any
of its presently outstanding securities or any of its securities which may
hereafter be issued.

     (g)  Exempt Transaction.  Subject to the accuracy of the Warrantholder's
representations in Section 10 hereof, the issuance of the Common Stock upon
exercise of this Warrant will constitute a transaction exempt from (i) the
registration requirements of Section 5 of the 1933 Act, in reliance upon Section
4(2) thereof, and (ii) the qualification requirements of the Illinois Securities
Act of 1953, in reliance upon Section 4(C) thereof.

     (h)  Compliance with Rule 144.  At the written request of the
Warrantholder, who proposes to sell Common Stock issuable upon the exercise of
the Warrant in compliance with Rule 144 promulgated by the Securities and
Exchange commission, the Company shall furnish to the Warrantholder, within ten
days after receipt of such request, a written statement confirming the company's
compliance with the filing requirements of the Securities and Exchange
Commission as set forth in such Rule, as such Rule may be amended from time to
time.


10.  REPRESENTATIONS AND COVENANTS OF THE WARRANTHOLDER.

     This Warrant Agreement has been entered into by the Company in reliance
upon the following representations and covenants of the Warrantholder:

     (a)  Investment Purpose.  The right to acquire Common Stock or the Common
Stock issuable upon exercise of the Warrantholder's rights contained herein will
be acquired for investment and not with a view to the sale or distribution of
any part thereof, and the Warrantholder has no present intention of selling or
engaging in any public distribution of the same except pursuant to a
registration or exemption.

     (b)  Private Issue.  The Warrantholder understands (i) that the Common
Stock issuable upon exercise of this Warrant is not registered under the 1933
Act or qualified under applicable state securities laws on the ground that the
issuance contemplated by this Warrant Agreement will be exempt from the
registration and qualifications requirements thereof, and (ii) that the
Company's reliance on such exemption is predicated on the representations set
forth in this Section 10.

     (c)  Disposition of Warrantholder's Rights.  In no event will the
Warrantholder make a disposition of any of its rights to acquire Common Stock or
the Common Stock issuable upon exercise of such rights unless and until (i) it
shall have notified the company of the proposed disposition, and (ii) if
requested by the Company, it shall have furnished the Company with an opinion of
counsel (which counsel may either be inside or outside counsel to the

                                       7
<PAGE>

Warrantholder) satisfactory to the Company and its counsel to the effect that
(A) appropriate action necessary for compliance with the 1933 Act has been
taken, or (B) an exemption from the registration requirements of the 1933 Act is
available. Notwithstanding the foregoing, the restrictions imposed upon the
transferability of any of its rights to acquire Common Stock or Common Stock
issuable on the exercise of such rights do not apply to transfers from the
beneficial owner of any of the aforementioned securities to its nominee or from
such nominee to its beneficial owner, and shall terminate as to any particular
share of Common Stock when (1) such security shall have been effectively
registered under the 1933 Act and sold by the holder thereof in accordance with
such registration or (2) such security shall have been sold without registration
in compliance with Rule 144 under the 1933 Act, or (3) a letter shall have been
issued to the Warrantholder at its request by the staff of the Securities and
Exchange Commission or a ruling shall have been issued to the Warrantholder at
its request by such commission stating that no action shall be recommended by
such staff or taken by such Commission, as the case may be, if such security is
transferred without registration under the 1933 Act in accordance with the
conditions set forth in such letter or ruling and such letter or ruling
specifies that no subsequent restrictions on transfer are required. Whenever the
restrictions imposed hereunder shall terminate, as hereinabove provided, the
Warrantholder or holder of a share of Common Stock then outstanding as to which
such restrictions have terminated shall be entitled to receive from the Company,
without expense to such holder, one or more new certificates for the Warrant or
for such shares of Common Stock not bearing any restrictive legend.

     (d)  Financial Risk.  The Warrantholder has such knowledge and experience
in financial and business matters as to be capable of evaluating the merits and
risks of its investment, and has the ability to bear the economic risks of its
investment.

     (e)  Risk of No Registration.  The Warrantholder understands that if the
Company does not register with the Securities and Exchange Commission pursuant
to Section 12 of the 1933 Act, or file reports pursuant to Section 15(d) of the
Securities Exchange Act of 1934 (the "1934 Act"), or if a registration
statement covering the securities under the 1933 Act is not in effect when it
desires to sell (i) the rights to purchase Common Stock pursuant to this Warrant
Agreement, or (ii) the Common Stock issuable upon exercise of the right to
purchase, it may be required to hold such securities for an indefinite period.
The Warrantholder also understands that any sale of its rights of the
Warrantholder to purchase Common Stock or Common stock which might be made by it
in reliance upon Rule 144 under the 1933 Act may be made only in accordance with
the terms and conditions of that Rule.

11.  TRANSFERS.  Subject to the terms and conditions contained in Section 10
hereof, this Warrant Agreement and all rights hereunder are transferable in
whole or in part by the Warrantholder and any successor transferee, provided,
however, in no event shall the number of transfers of the rights and interests
in all of the Warrants exceed three (3) transfers, and no such transfer shall be
effected to an entity the Company considers a competitor or to any other entity
which has an affiliate which the Company considers a competitor. The transfer
shall be recorded on the books of the Company upon receipt by the Company of a
notice of transfer in the form attached hereto as Exhibit II (the "Transfer
Notice"), at its principal offices and the payment to the Company of all
transfer taxes and other governmental charges imposed on such transfer. The
Warrantholder considers the foregoing to be a reasonable restraint.

                                       8
<PAGE>

12.  MISCELLANEOUS.

     (a)  Effective Date.  The provisions of this Warrant Agreement shall be
construed and shall be given effect in all respects as if it had been executed
and delivered by the Company on the date hereof. This Warrant Agreement shall be
binding upon any successors or assigns of the Company.

     (b)  Attorney's Fees.  In any litigation, arbitration or court proceeding
between the Company and the Warrantholder relating hereto, the prevailing party
shall be entitled to attorneys' fees and expenses and all costs of proceedings
incurred in enforcing this Warrant Agreement.

     (c)  Governing Law.  This Warrant Agreement shall be governed by and
construed for all purposes under and in accordance with the laws of the State of
Illinois.

     (d)  Counterparts.  This Warrant Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     (e)  Notices.  Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery, facsimile
transmission (provided that the original is sent by personal delivery or mail as
hereinafter set forth) or seven (7) days after deposit in the United States
mail, by registered or certified mail, addressed (i) to the Warrantholder at
6111 North River Road, Rosemont, Illinois 60018, attention: James Labe, Venture
Leasing Director, cc: Legal Department, (and/or, if by facsimile, (847) 518-5465
and (ii) to the Company at 676 N. St. Clair, Suite 900, Chicago, IL 60611,
(and/or if by facsimile, (312) 867-5100 or at such other address as any such
party may subsequently designate by written notice to the other party.

     (f)  Remedies.  In the event of any default hereunder, the non-defaulting
party may proceed to protect and enforce its rights either by suit in equity
and/or by action at law, including but not limited to an action for damages as a
result of any such default, and/or an action for specific performance for any
default where Warrantholder will not have an adequate remedy at law and where
damages will not be readily ascertainable. The Company expressly agrees that it
shall not oppose an application by the Warrantholder or any other person
entitled to the benefit of this Agreement requiring specific performance of any
or all provisions hereof or enjoining the Company from continuing to commit any
such breach of this Agreement.

     (g)  No Impairment of Rights.  The Company will not, by amendment of its
Charter or through any other means, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
actions as may be necessary or appropriate in order to protect the rights of the
Warrantholder against impairment.

     (h)  Survival.  The representations, warranties, covenants and conditions
of the respective parties contained herein or made pursuant to this Warrant
Agreement shall survive the execution and delivery of this Warrant Agreement.

     (i)  Severability.  In the event any one or more of the provisions of this
Warrant Agreement shall for any reason be held invalid, illegal or
unenforceable, the remaining provisions of this Warrant Agreement shall be
unimpaired, and the invalid, illegal or unenforceable provision shall be
replaced by a mutually acceptable valid, legal and enforceable provision,

                                       9

<PAGE>

which comes closest to the intention of the parties underlying the invalid,
illegal or unenforceable provision.

     (j)  Amendments.  Any provision of this Warrant Agreement may be amended by
a written instrument signed by the Company and by the Warrantholder.

     IN WITNESS WHEREOF, the parties hereto have caused this Warrant Agreement
to be executed by its officers thereunto duly authorized as of the Effective
Date.

                                       Company OPEN PORT TECHNOLOGY, INC.

                                       By: /s/ David C. Aniol
                                           ------------------------------------

                                       Title: CFO
                                              ---------------------------------

                                       Warrantholder: COMDISCO, INC.

                                       By:
                                           ------------------------------------

                                       Title:
                                              ---------------------------------

                                      10