<PAGE>   1
                                                                   EXHIBIT 10.19

                              SYMPOSIUM CORPORATION
                                 410 PARK AVENUE
                                    SUITE 830
                            NEW YORK, NEW YORK 10022



                                          July 18, 2000

Lancer Offshore Inc.
Kaya Flamboyan 9
Curacao, Netherlands Antilles

Capital Research, Ltd.
27241 Paseo Peregrino
San Juan Capo, California  92675

Mr. Gary Herman
c/o GHM, Inc.
74 Trinity Place, 20th Floor
New York, New York  10006

Mr. Joseph Giamanco
c/o GHM, Inc.
74 Trinity Place, 20th Floor
New York, New York  10006

Gentlemen:

      Reference is made to the Certificate of Designation (the "Certificate")
creating the series of preferred stock of Symposium Corporation, a Delaware
corporation (the "Company"), designated as the Series C Convertible Preferred
Stock, par value $.001 per share (the "Series C Shares"), the Term Sheet (the
"Term Sheet") describing the terms upon which the Series C Shares were offered
and sold to each of you (the "Series C Holders") and the Letter Agreements,
dated as of April 24, 2000 (the "April 24 Agreement") and May 30, 2000 (the "May
30 Agreement") to which we are parties. The Certificate, the Term Sheet, the
"April 24 Agreement and the May 30 Agreements are hereinafter collectively
referred to as the "Documents."

      This letter (the "Letter Agreement") sets forth our agreement as follows:

            1. The Documents provide that, if the Company fails to redeem the
Series C Shares in full on or prior to December 26, 2000 (such failure, a
"Redemption Default"), the conversion price of the Series C Shares (the
"Conversion Price") shall be reduced to $0.25 per share. By their execution and
delivery hereof, the Series C Holders hereby agree that the
<PAGE>   2
occurrence of a Redemption Default shall not trigger any reduction in the
Conversion Price from the price in effect immediately prior to such Redemption
Default. Accordingly, notwithstanding any provision of the Documents to the
contrary, upon conversion of the Series C Preferred Stock (whether such
conversion occurs prior to, on or subsequent to December 26, 2000), the
effective Conversion Price will be continue to be $1.00 per share (subject to
anti-dilution adjustments as provided in the Documents upon the occurrence of
any of the events described therein).

            2. The Series C Holders hereby confirm that, by their execution and
delivery of this Letter Agreement, they irrevocably waive any default by the
Company under the Documents arising out of or relating to the failure by the
Company to issue Conversion Shares at a Conversion Price of $0.25 per share
following a Redemption Default by the Company.

            3. Each Series C Holder agrees that it will not transfer any Series
C Shares unless and until (a) the proposed transferee has agreed in writing to
be bound by the agreements of the Series C Holders and waivers of such Holders
set forth in the April 24 Agreement and the May 30 Agreement, as well as
provisions of paragraphs 1 and 2 above fully and to the same extent as the
transferring Series C Holder is so bound and (b) the transferring Series C
Holder has caused a copy of such agreement to be delivered to the Company. Any
transfer in violation of the immediately preceding sentence will be void and
will not be recognized by the Company.

            4. In consideration for the agreements of each Holder set forth
herein, the Company hereby agrees to issue to each Holder, promptly following
the execution and delivery of this Letter, an aggregate of 1,523,750 shares of
Common Stock, pro rata in accordance with the respective numbers of shares of
Series C Preferred Stock owned by each of them. The shares of Common Stock
issuable pursuant to this paragraph 3, together with the shares of Series C
Preferred Stock and Common Stock issuable to Capital Research Ltd. pursuant to
paragraph 4 below, are hereinafter referred to collectively as the "Additional
Shares." All Additional Shares issuable to the Holders (as well as the shares of
Common Stock into which the shares of Series C Preferred Stock issuable to
Capital Research Ltd. pursuant to paragraph 5 below are convertible) will be
entitled to the same registration rights as the shares of Common Stock issuable
to the Holders upon conversion of the Series C Shares pursuant to the Documents.

            5. In connection with the consummation of the transactions
contemplated by this Letter, the Company also agrees to pay a fee to Capital
Research Ltd. equal to $150,000, such fee to be payable through the issuance of
an aggregate of 1,500 shares of Series C Preferred Stock plus an "equity kicker"
of 50,000 shares of Common Stock.

            6. Except as expressly provided herein, the Documents will remain in
full force and effect as originally executed and delivered by the parties
hereto. This Letter Agreement supersedes any prior understanding or agreement,
written or oral, among the parties hereto relating to the subject matter hereof.

            7. Each of the Holders each hereby severally represents to the
Company, on behalf of itself, that such Holder is (and on each date of issuance
of such Additional Shares will be) an "accredited investor" within the meaning
of Regulation D, as promulgated by the Securities and Exchange Commission
pursuant to the Securities Act of 1933, as amended (the
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"Act"), and has such knowledge and experience in financial and business matters
that it is capable of evaluating the merits and risks of an investment in the
Additional Shares; that such Holder is acquiring the Additional Shares to be
issued to such Holder for investment and without a view to the sale, assignment,
transfer or other distribution thereof; the Additional Shares may not be offered
for sale, sold or otherwise transferred except pursuant to an effective
registration statement under the Act and in compliance with the applicable
securities laws of any state or other jurisdiction, or pursuant to an opinion of
counsel satisfactory to the Company that such registration is not required and
such compliance has been obtained. The Company may affix an appropriate legend
to any certificate(s) representing the Additional Shares to reflect the
foregoing.

            8. This Letter Agreement will be governed by the laws of the State
of New York applicable to contracts made and to be performed entirely within
such State. Any claims or disputes relating in any way to this Agreement shall
be submitted to the New York State courts or the United States District Court
for the Southern District of New York. The parties hereby consent to such venue
and the personal jurisdiction of such courts and agree not to contest such venue
or assert any claim to move the claim or dispute to another venue or forum.

            If the foregoing correctly sets forth our understanding, please so
indicate by signing an enclosed counterpart of this Letter Agreement and
returning it to the undersigned, whereupon it will constitute a binding
agreement between us. This Letter Agreement may be executed in counterparts and
by the parties hereto in separate counterparts, each of which shall constitute
an original and all of which together shall constitute one and the same
agreement.

                                    Very truly yours,

                                    SYMPOSIUM CORPORATION


                                    By:/s/ Ronald Altbach
                                       ------------------
                                       Ronald Altbach
                                        Chairman of the Board and Chief
                                        Executive Officer
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Accepted and agreed to as of the date first above written:

LANCER OFFSHORE, INC.


By: /s/ M. Lauer
    --------------------------------


CAPITAL RESEARCH, LTD.


By: /s/ Bruce D. Cowen
    -------------------------------


 /s/ Joseph Giamanco
----------------------------------
JOSEPH GIAMANCO


 /s/ Gary Herman
----------------------------------
GARY HERMAN





[Signature Page of Letter Agreement, dated as of July 18, 2000, among Symposium
Corporation and the Holders of the Series C Preferred Shares]
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                                                                    EXHIBIT 99.6


SYMPOSIUM                                      410 PARK AVENUE, SUITE 830
CORPORATION                                    NEW YORK, NEW YORK 10022-4407
                                               WWW.SYMPOSIUMCORP.COM
                                               TELEPHONE (212) 752-2601
                                               FAX             (212) 754-9906




August 3, 2000


Executive Management Services and
Rupert Galliers-Pratt
Bennet House
54 St. James Street
London, England

Dear Rupert,

This letter will confirm our mutual agreement to the following:

   1.  The Consulting Agreement dated as of January 1, 1999 between Symposium
Corporation ("Symposium") and Executive Management Services ("EMS") was
terminated effective January 28, 2000, except for the covenants of EMS and
Rupert Galliers-Pratt ("RGP") in Sections 6 and 7 thereof, which shall continue
and be binding for the full terms thereof.

   2.  As consideration for any and all amounts which may be owing to EMS or to
RGP under the Consulting Agreement, Symposium will pay to EMS and RPG the sum of
$250,000, payable (i) $105,000 on the date hereof, (ii) $15,000 per month for 9
months, beginning on August 31, 2000 and continuing on the last day of each
month through April 30, 2001, and (iii) a final payment of $10,000 on May 31,
2001.

   3.  Symposium will pay RGP's past travel expenses itemized on Schedule I
attached.

   4.  The only Symposium stock options granted to EMS or RGP which have vested
are the options for 200,000 shares granted to EMS on December 3, 1998. All other
Symposium stock options previously granted to EMS or RGP have not vested and
have terminated.

   5.  Symposium will issue to Executive Management Services a warrant to
purchase 125,000 shares of Symposium common stock at a price of $2.50 per share.

   6.  RGP will cause UK Value ("UKV"), a U.K. company, to issue to Symposium
a warrant to purchase 125, 000 shares of UKV's, common stock at a price of L1
per share.
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   7. (a) In consideration of this agreement and for other good and valuable
consideration, Symposium for itself and its successors and assigns hereby
releases, remises and forever discharges EMS and RGP, their respective heirs,
executors, predecessors, successors and assigns, and each and every of EMS's
past, present and future parents, subsidiaries, affiliates and divisions, as
applicable, from any and all actions, causes of action, claims, demands, rights,
suits, accountings, debts, duties, dues, accounts, bonds, covenants, contracts,
agreements, duties and obligations of whatsoever kind or nature, whether at law
or equity, or otherwise known or unknown, by reason of any matter or thing
whatsoever which Symposium has or had against any of them except for (i) EMS's
and RGP's obligations under this agreement and (ii) EMS's and RGP's obligations
under Sections 6 and 7 of the Consulting Agreement.

      (b) In consideration of this agreement, and for other good and valuable
consideration, EMS and RGP for themselves and their respective parents,
subsidiaries, affiliates and predecessors, and the heirs, executors,
representatives, successors and assigns of the foregoing, hereby release, remise
and forever discharge Symposium, its predecessors, successors (by merger or
otherwise) and assigns, and each and every of their respective past, present and
future parents, subsidiaries and affiliates, as applicable, in which any of them
has, had or may have any interest, and the present and future directors,
officers, employees, agents, professional advisers, servants and shareholders of
each and every one of them, as applicable, from any and all actions, causes of
action, claims, demands, rights, suits, accountings, debts, duties, dues,
accounts, bonds, covenants, contracts, agreements, duties and obligations of
whatsoever kind or nature, whether at law or equity, or otherwise known or
unknown by reason of any matter or thing whatsoever which any of them has or had
against any of them, except for obligations under this agreement.

   8. (a)  All notices, requests, demands and other communications given
pursuant to this agreement shall be given and effective as provided in the
Consulting Agreement.

      (b) This agreement contains the sole and entire agreement and
understanding of the parties with respect to the entire subject matter of this
agreement, and any and all prior discussions, negotiations, commitments and
understandings, whether oral or otherwise, related to the subject matter of this
agreement are hereby merged herein. No representations, oral or otherwise,
express or implied, other than those contained in this agreement have been
relied upon by any party to this agreement. This agreement can only be amended
in writing signed by all of the parties.

      (c) In the event that any provision or portion of this agreement shall be
determined to be invalid or unenforceable for any reason, in whole or in part,
the remaining provisions of this agreement shall be unaffected thereby and shall
remain in full force and effect to the fullest extent permitted by law.

      (d) This agreement has been made and entered into in the State of New York
and shall be construed in accordance with the laws of the State of New York,
without regard to conflict of law principles. The state and federal courts
located in Manhattan, New York City, New York shall have exclusive jurisdiction
over all disputes arising out of this agreement and the parties hereto consent
to such jurisdiction and venue.

      (e) The various captions of this agreement are for reference only and
shall not be considered or referred to in resolving questions of interpretation
of this agreement.

      (f) This agreement may be executed in any number of counterparts, each of
which shall be deemed to be an original, but all of which together shall
constitute one and the same instrument.
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      (g) If any action or proceeding is brought to enforce or interpret any
provision of this agreement, the prevailing party shall be entitled to recover
as an element of its costs, and not its damages, its reasonable attorneys' fees,
costs and expenses. The prevailing party is the party who is entitled to recover
its costs in the action or proceeding. A party not entitled to recover its costs
may not recover attorneys' fees. No sum for attorneys' fees shall be counted in
calculating the amount of a judgment for purposes of determining whether a party
is entitled to recover its costs or attorneys' fees.

      (h) All capitalized terms used and not defined herein shall have the
meanings given them in the Consulting Agreement.

      (i) No failure to exercise or delay in exercising any right, power or
remedy shall constitute a waiver thereof or of any other right, power or remedy;
any such waiver can only be made expressly and in writing.

                                    Sincerely,



                                    By: /s/ Ronald Altbach
                                       -----------------------------------------
                                            Ronald Altbach
                                            Chief Operating Officer

                                    Accepted and Agreed:

                                    Executive Management Services



                                    By: /s/ Rupert Galliers-Pratt
                                       -----------------------------------------
                                    Its: on behalf of Executive Management
                                               Services

Witness:



                                      /s/ Rupert Galliers-Pratt
                                    --------------------------------------------
                                    Rupert Galliers-Pratt