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                                                                     EXHIBIT 4.4

                                                                  EXECUTION COPY

                           TRADEMARK LICENSE AGREEMENT

                  This Trademark License Agreement ("Agreement") is entered into
as of September 2, 2003 (the "Effective Date") by and among Elron Electronic
Industries Ltd., an Israeli corporation, having its principal place of business
at 3 Azrieli Center, 42 Floor, Tel Aviv, Israel 67023 ("Elron Electronic") and
Elron Software, Inc., a Delaware corporation, having its principal place of
business at One Burlington Business Center, 67 South Bedford Street, Burlington,
Massachusetts 01803-0977 ("Elron Software") (Elron Electronic and Elron Software
collectively referred to as "Licensor"), and Zix Corporation, a Texas
corporation, having its principal place of business at 2711 N. Haskell Avenue,
Suite 2300, LB 36, Dallas, Texas 75204-2960 ("Zix"), together with its
Affiliates (Zix and its Affiliates collectively referred to as "Licensee").

                  WHEREAS, Licensor is the owner of the Licensed Mark (as
defined below);

                  WHEREAS, pursuant to that certain Asset Purchase Agreement
dated September 2, 2003 (the "Asset Purchase Agreement"), by and among Zix, Zix
Acquisition Corporation, a Delaware corporation and wholly owned subsidiary of
Zix ("Purchaser Sub"), Elron Electronic, Elron Software and Elron Software
(2000) Ltd., an Israeli corporation and wholly owned subsidiary of Elron
Software ("Elron 2000"), Zix or Purchaser Sub is acquiring certain assets from
Elron Software and Elron 2000; and

                  WHEREAS, in accordance with the Asset Purchase Agreement and
in partial consideration of the amounts paid by Zix under the Asset Purchase
Agreement, Licensor agrees to grant Licensee, and Licensee desires to receive
from Licensor, a license to use the Licensed Mark in connection with such assets
and Licensee's business and business activities in the Field of Use (as defined
below).

                  NOW THEREFORE, in consideration of the mutual covenants and
promises contained herein, the parties hereto agree as follows:

1.       DEFINITIONS.

         1.1      "Affiliate" shall mean (i) any wholly-owned subsidiary of Zix
or (ii) upon the prior written consent of Elron Electronic (which shall not be
unreasonably withheld), any other corporation, partnership or other entity that,
directly or indirectly, controls, is controlled by or is under common control
with Zix, for so long as such control exists. For purposes of the foregoing,
"control" shall mean (a) possessing, directly or indirectly, the power to direct
or cause the direction of the management and policies of such corporation,
partnership or entity, (b) having direct or indirect ownership of more than
fifty percent (50%) of the voting power of all outstanding shares entitled to
vote at a general election of directors of such corporation, partnership or
entity or (c) having direct or indirect ownership of more than fifty percent
(50%) of the equity interest in a partnership or limited liability company.

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         1.2      "Field of Use" shall mean all computer programs for and
services related to (a) tracking, reporting and/or screening of web sites, (b)
filtering, monitoring or blocking communications via electronic mail, newsgroups
and/or ftp sites, (c) analyzing and/or improving usage of computer channels, (d)
development of operations support systems and/or network operation centers, (e)
electronic messaging protection or transactions to protect against viruses,
spam, and/or electronic attack, and/or (f) secure electronic communications,
such as, without limitation, electronic mail encryption and electronic
prescribing.

         1.3      "Licensed Mark" shall mean the mark "ELRON SOFTWARE", and all
trademark and service mark applications and registrations for such mark
worldwide.

2.       LICENSE GRANT.

         2.1      License Grant. Subject to the terms and conditions of this
Agreement, Licensor hereby grants to Licensee a worldwide, exclusive,
non-transferable, non-sublicensable, royalty-free, fully-paid up license to use
the Licensed Mark solely in connection with Licensee's business and business
activities in the Field of Use (including, without limitation, as Licensee's
d/b/a name, fictitious business name, tradename, trademarks, service marks and
logos, or any part of any of the foregoing).

         2.2      Ownership. Licensee acknowledges that, except as set forth
herein, Licensee has no rights, title or interest in or to the Licensed Mark and
that all use of the Licensed Mark by Licensee shall inure to the benefit of
Licensor.

         2.3      No Warranty. The grant of rights hereunder by Licensor to the
Licensed Mark is made only to the extent of the rights actually held by Licensor
in such Licensed Mark. Licensor makes no warranty, express or implied, and
hereby disclaims all warranties, with respect thereto or with respect to the
rights of any third parties that may conflict with the rights granted hereunder.

3.       QUALITY STANDARDS.

         3.1      Quality Control. (a) Licensor shall have the right to exercise
quality control over Licensee's use of the Licensed Mark, including over the
materials, products and services which are actually or planned to be offered,
sold, marketed, distributed or provided ("Offered") by Licensee under the
Licensed Mark, and to the degree deemed reasonably necessary by Licensor to
maintain the validity and enforceability of the Licensed Mark and to protect the
goodwill associated therewith, as set forth below. Licensor acknowledges that
the quality of the materials, products and services Offered by Licensor through
Elron Software's business as of the Effective Date is adequate for this purpose.
Accordingly, Licensee acknowledges and is familiar with the standards, quality,
style and image of Licensor, and shall at all times during the Term use the
Licensed Mark in a manner that is consistent therewith. Each of the provisions
of this Agreement relating to the proper use and protection of the Licensed
Mark, and of the goodwill associated therewith, is a material provision of this
Agreement.

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         (b) For Licensor's trademark quality control purposes, upon Licensor's
reasonable prior written request, Licensee shall furnish to Licensor a sample of
products and materials bearing the Licensed Mark that Licensee then currently
distributes or intends to distribute. If Licensor reasonably and in good faith
believes the samples bearing the Licensed Mark do not meet the Minimum Quality
Threshold (as defined below), Licensor shall notify Licensee in writing, and
Licensee shall have a reasonable period of time to make the changes and/or
corrections that the parties mutually agree are reasonably necessary to protect
the Licensed Mark. For purposes of this Agreement, "Minimum Quality Threshold"
shall mean the level of quality, existing as of the Effective Date, of
Licensor's products distributed and services provided under the Licensed Mark.

         3.2      Compliance With Laws. Licensee agrees to comply with all
applicable local, state and federal laws relating to Licensee's activities under
this Agreement.

         3.3      Proprietary Notices. All advertising and promotional materials
and all other electronic, printed and written materials using the Licensed Mark
shall state that such Licensed Mark is owned by Elron Software (or any
successor thereof) or Elron Electronic, as instructed by Licensor. Licensee
agrees to use the following form of such notice, which Licensor may change from
time to time upon reasonable prior written notice to Licensee:

         [LICENSED MARK]* is a [trademark][service mark] of [Licensor] and is
         used by [Licensee] under license from [Licensor].

         Where "*" indicates the symbol "(R)" where the Licensed Mark is the
subject of a registration issued by the United States Patent and Trademark
Office, and indicates the symbol "(TM)" or "(SM)", as appropriate, where the
Licensed Mark is not the subject of such a registration.

4.       TERM AND TERMINATION.

         4.1      Term. This Agreement shall commence as of the Effective Date
and shall continue in effect through December 31, 2005, unless terminated in
accordance with the terms and conditions set forth below. Licensee shall use
good faith, reasonable efforts to transition away from using the Licensed Mark
as soon as reasonably practicable consistent with its business and business
activities in the Field of Use. If Licensee abandons all use of the Licensed
Mark for a period of at least 60 consecutive days, this Agreement shall
automatically terminate unless Licensor and Licensee otherwise agree within 10
days of the end of such 60-day period.

         4.2      Termination By Licensor or Licensee. Licensor or Licensee may
terminate this Agreement in the event the other breaches any material term of
this Agreement and fails to cure such breach within sixty (60) days after
receipt of written notice from the terminating party describing such breach. In
addition, Licensor may terminate this Agreement if Licensee (i) makes a general
assignment for the benefit of its creditors, (ii) institutes proceedings to be
adjudicated a voluntary bankrupt, or consents to the filing of a petition of
bankruptcy against it and such proceedings or petition are not

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dismissed within sixty (60) days, (iii) seeks reorganization under any
bankruptcy act, or consents to the filing of a petition seeking such
reorganization, or (iv) has a decree entered against it by a court of competent
jurisdiction appointing a receiver, liquidator, trustee or assignee in
bankruptcy or in insolvency covering all or substantially all of its property
or providing for the liquidation of its property or business affairs, and such
decree is not vacated within sixty (60) days.

         4.3      Termination By Licensee. This Agreement may be terminated by
Licensee without cause upon thirty (30) days' prior written notice to Licensor.

         4.4      Effect of Termination. In the event of any termination of this
Agreement: (a) Licensee shall have a reasonable period of time, but in no event
longer than 60 days, to change its d/b/a name, fictitious business name,
tradename, trademarks, services marks and logos that include the Licensed Mark
and to deplete its existing inventory of, or modify or destroy, any letterhead,
materials, literature and products that bear the Licensed Mark; and (b) Sections
4.4, 6, 7 and 8 shall survive such termination.

5.       PROTECTION, MAINTENANCE AND ENFORCEMENT.

         5.1      Prosecution and Maintenance. In order to protect the Licensed
Mark in the countries in which the Licensed Mark is the subject of a
registration or pending application existing as of the Effective Date, Licensor
agrees to (a) diligently prosecute all such pending applications to
registration, (b) maintain all registrations existing as of the Effective Date
and all registrations issuing on the pending applications existing as of the
Effective Date (including, without limitation, filing all relevant documents and
specimens and paying all applicable maintenance fees); provided, however, that
Licensee agrees to reasonably assist Licensor in such activities and provided
further that any expenses incurred in connection with such activities shall be
borne by Licensor.

         5.2      Enforcement. Licensee agrees to reasonably cooperate with and
assist Licensor in protecting and defending the Licensed Mark and shall promptly
notify Licensor in writing of any infringements, claims or actions by others in
derogation of the Licensed Mark of which Licensee becomes aware. Licensor shall
promptly take such commercially reasonable legally permissible action as
necessary to protect and defend the Licensed Mark. Licensee shall not take any
action on account of any such infringement, claim or action without the prior
written consent of Licensor, which consent shall not be unreasonably withheld or
delayed.

6.       LIMITATION OF LIABILITY.

         NOTWITHSTANDING ANYTHING ELSE IN THIS AGREEMENT OR OTHERWISE, NO PARTY
WILL BE LIABLE TO ANY OTHER PARTY OR ANY OTHER PERSON OR ENTITY WITH RESPECT TO
ANY SUBJECT MATTER OF THIS AGREEMENT UNDER ANY CONTRACT, NEGLIGENCE, STRICT
LIABILITY OR OTHER LEGAL OR EQUITABLE THEORY FOR ANY INDIRECT, INCIDENTAL,
SPECIAL OR CONSEQUENTIAL DAMAGES, EVEN IF THE REMEDIES PROVIDED FOR IN THIS
AGREEMENT FAIL OF THEIR ESSENTIAL

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PURPOSE AND EVEN IF EITHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OR
PROBABILITY OF SUCH DAMAGES.

7.       GENERAL.

         7.1      Independent Contractors. The parties hereto are independent
contractors and are not partners, joint venturers or otherwise affiliated. No
party has any right or authority to bind any other party in any way without the
prior written consent of such other party.

         7.2      Assignment. No party may assign this Agreement without the
prior written consent of each of the other parties, except that a party may,
without the prior written consent of all of the other parties, assign this
Agreement to a successor of all or substantially all of such party's assets,
stock or business to which this Agreement relates (whether by sale, acquisition,
merger, operation of law or otherwise).

         7.3      Notices. All notices, requests, demands and other
communications required or permitted to be given under this Agreement shall be
in writing and shall be deemed to have been duly given only if personally
delivered, delivered by an overnight courier service with tracking capabilities
and costs prepaid, or mailed by certified or registered mail, return receipt
requested, postage prepaid, to a party at the address set forth below or such
other address as a party last provided to the other by written notice pursuant
to this Section 8.3:

If to Elron Electronic Industries Ltd.:

                  Elron Electronic Industries Ltd.
                  3 Azrieli Center, 42nd Floor
                  Tel Aviv, Israel 67023
                  Attention: Legal Department

If to Elron Software, Inc.:

                  Elron Software, Inc.
                  c/o Elron Electronic Industries Ltd.
                  3 Azrieli Center, 42nd Floor
                  Tel Aviv, Israel 67023
                  Attention: Legal Department

If to Licensee:

                  Zix Corporation
                  2711 N. Haskell Avenue
                  Suite 2300, LB 36
                  Dallas, Texas 75204-2960
                  Attention: Legal Department

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         7.4      Amendment, Modification and Waiver. Any amendment or
modification of this Agreement or any waiver of any breach of any term or
condition of this Agreement must be in a writing signed by all of the parties in
order to be effective and shall not be construed as a waiver of any continuing
or succeeding breach of such term or condition, a waiver of the term or
condition itself or a waiver of any right under this Agreement. The failure of
any party to enforce its rights or to require performance by any of the other
parties of any term or condition of this Agreement shall not be construed as a
waiver of such rights or of its right to require future performance of that term
or condition.

         7.5      Successors and Assigns. This Agreement shall be binding upon,
and inure to the benefit of, the parties' respective successors and valid
assigns.

         7.6      Governing Law. This Agreement shall be governed by and
interpreted under the laws of the State of New York without regard to the
conflicts of law provisions thereof.

         7.7      Headings. Headings and captions are for convenience of
reference only and shall not be used in the interpretation of this Agreement.

         7.8      Severability. In the event that any provision of this
Agreement shall be determined by a court of competent jurisdiction to be illegal
or unenforceable, that provision will be limited or eliminated to the minimum
extent necessary so that this Agreement shall otherwise remain in full force and
effect and enforceable.

         7.9      Entire Agreement. This Agreement (including all exhibits
attached hereto) and the Asset Purchase Agreement constitute the entire
understanding and agreement between the parties with respect to the subject
matter hereof and supersedes all discussions, negotiations, agreements and past
dealings, either oral or written, between or among the parties relating to the
subject matter hereof.

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         IN WITNESS WHEREOF, the parties hereto have each caused this Agreement
to be executed by their authorized representatives as of the Effective Date.

                                    ZIX CORPORATION

                                    By: /s/ RONALD A. WOESSNER
                                        ----------------------------------------
                                    Name: Ronald A. Woessner
                                          --------------------------------------
                                    Title: SVP
                                           -------------------------------------

                                    ELRON ELECTRONIC INDUSTRIES LTD.

                                    By: /s/ DORAN BIRGER
                                        ----------------------------------------
                                    Name: Doran Birger
                                          --------------------------------------
                                    Title: President & CEO
                                           -------------------------------------

                                    By: /s/ PAUL WEINBERG
                                        ----------------------------------------
                                    Name: Paul Weinberg
                                          --------------------------------------
                                    Title: General Counsel & Corp Secretary
                                           -------------------------------------

                                    ELRON SOFTWARE, INC.

                                    By: /s/ ADAM N. BOSNIAN
                                        ----------------------------------------
                                    Name: Adam N. Bosnian
                                          --------------------------------------
                                    Title: Co-General Manager
                                           -------------------------------------

                                    By: /s/ HENRY R. TUMBLIN
                                        ----------------------------------------
                                    Name: Henry R. Tumblin
                                          --------------------------------------
                                    Title: Co-General Manager
                                           -------------------------------------<PAGE>
                                                                     EXHIBIT 4.4

                                 AMENDMENT NO. 3

                                       TO

                          REGISTRATION RIGHTS AGREEMENT

      Amendment No. 3 to Registration Rights Agreement (this "Amendment"), dated
September 5, 2003, by and between Alfred I. DuPont Testamentary Trust (the
"Trust") and The St. Joe Company, a Florida corporation (the "Company").

      1. Introduction. The Trust and the Company have entered into a
Registration Rights Agreement, dated as of December 16, 1997, Amendment No. 1
thereto, dated as of January 26, 1998, and an Amendment No. 2 thereto, dated May
24, 2002 (as amended, the "Registration Rights Agreement"), which governs, among
other things, certain terms and conditions of the sale of Shares of the
Company's Common Stock Beneficially Owned by the Trust, from time to time, in
registered public offerings. The Company has filed a Registration Statement on
Form S-3 (No. 333-108292) with the Securities and Exchange Commission on August
28, 2003 (the "Registration Statement") with respect to the sale by the Trust,
from time to time, of certain Shares of the Company's Common Stock Beneficially
Owned by the Trust. In connection with such sales, the Trust and the Company
believe that it is in their best interests to effect certain amendments to the
Registration Rights Agreement, as prescribed below.

      2. Definitions. Capitalized terms used but not otherwise defined herein
shall have the respective meanings ascribed to them in the Registration Rights
Agreement.

      3. Provisions Applicable to the Registration Statement. The Company shall
have all obligations applicable to a Demand Registration with respect to the
Registration Statement; provided, however, that in the event the Trust sells
Shares of Common Stock Beneficially Owned by the Trust and covered by the
Registration Statement, the Registration Statement (including all amendments
thereto and all supplemental prospectuses included therein) shall count as one
Demand Registration of the Trust and, with respect to any sale of such Shares
covered by the Registration Statement requiring a prospectus supplement after
the initial sale of shares covered by the Registration Statement (and the
exercise of any over-allotment option with respect thereto), the Trust shall
reimburse the Company for any incremental out-of-pocket expenses incurred by the
Company in connection with such sale, including, without limitation, all
printing expenses with respect to such sale.

      4. Effectiveness of this Amendment. This Amendment shall become effective
upon its execution by the Company and the Trust.

      5. Agreement in Full Force and Effect. Except as amended by the terms of
this amendment, the Registration Rights Agreement shall remain in full force and
effect in accordance with its terms.

      6. Counterparts. This Amendment may be executed simultaneously in any
number of counterparts, each of which shall be deemed an original, but all of
such counterparts shall together constitute one and the same instrument.

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      IN WITNESS WHEREOF, the parties have caused this Amendment to be executed
and delivered by the respective officers thereunto duly authorized as of the
date first written above.

                                              ALFRED I. DUPONT TESTAMENTARY
                                              TRUST

                                              By: ______________________________
                                                    W. L. Thornton, Trustee

                                              THE ST. JOE COMPANY

                                              By: ______________________________
                                                    Peter S. Rummell
                                                    Chairman and CEO

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