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                                                                     EXHIBIT 4.2
                                                                  EXECUTION COPY

                          REGISTRATION RIGHTS AGREEMENT

         REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT"), dated as of July 22,
2003, by and between Zix Corporation, a Texas corporation, with its headquarters
located at 2711 North Haskell Avenue, Suite 2300 LB36, Dallas, Texas 75204 (the
"COMPANY"), and PocketScript L.L.C., an Ohio limited liability company (the
"SELLING SHAREHOLDER").

         WHEREAS:

         A.       In connection with an Asset Purchase Agreement between the
parties dated of even date herewith (the "ASSET PURCHASE AGREEMENT"), the
Company has agreed, upon the terms and subject to the conditions contained
therein, to issue and sell to the Selling Shareholder the shares of its Common
Stock, par value $.01 per share (the "COMMON STOCK") referenced in Section 4.1
of the Asset Purchase Agreement; and

         B.       To induce the Selling Shareholder to execute and deliver the
Asset Purchase Agreement, the Company has agreed to provide certain registration
rights under the Securities Act of 1933, as amended, and the rules and
regulations thereunder, or any similar successor statute (collectively, the
"1933 ACT"), and applicable state securities laws;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Selling Shareholder hereby agrees as follows:

                                    ARTICLE I.
                                   DEFINITIONS

         Section 1.1. As used in this Agreement, the following terms shall have
the following meanings:

                  (a)      "SELLING SHAREHOLDER" means the Selling Shareholder.

                  (b)      "REGISTER," "REGISTERED," and "REGISTRATION" refer to
         a registration effected by preparing and filing a Registration
         Statement or Statements in compliance with the 1933 Act and pursuant to
         Rule 415 under the 1933 Act or any successor rule providing for
         offering securities on a continuous basis ("RULE 415"), and the
         declaration or ordering of effectiveness of such Registration Statement
         by the United States Securities and Exchange Commission (the "SEC").

                  (c)      "REGISTRABLE SECURITIES" means shares of Common Stock
         being issued to the Selling Shareholder pursuant to the Asset Purchase
         Agreement.

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                  (d)      "REGISTRATION STATEMENT(s)" means a registration
         statement(s) of the Company under the 1933 Act.

         Section 1.2. Capitalized terms used herein and not otherwise defined
herein shall have the respective meanings set forth in the Asset Purchase
Agreement.

                                   ARTICLE II.
                                  REGISTRATION

         Section 2.1.      REGISTRATION. The Company shall prepare, and, on or
prior to the date (the "FILING DATE") that is the later of (i) thirty (30)
calendar days after the Closing or (ii) two business days following the
effectiveness of that certain registration statement (the "Equity Financing
Registration Statement") to be filed with respect to the equity financing
completed by the Company in June 2003, as reported in the Company's Current
Report on Form 8-K dated June 25, 2003 and filed with Securities and Exchange
Commission, file with the SEC a Registration Statement on Form S-3 (or, if Form
S-3 is not then available, on such form of Registration Statement as is then
available to effect a registration of the Registrable Securities, subject to the
consent of the Selling Shareholder, which consent will not be unreasonably
withheld, conditioned or delayed) covering the resale of the Registrable
Securities. The Company shall provide a draft of the Registration Statement to
counsel for the Selling Shareholder prior to its filing or other submission so
that such counsel has a reasonable opportunity to review and comment on the
Registration Statement prior to it being filed. The Company shall use all
commercially reasonable efforts to obtain effectiveness of the Registration
Statement as soon as possible thereafter. The Company shall file the Equity
Financing Registration Statement on or before July 24, 2003, and shall use
commercially reasonable efforts to cause it to become effective as soon as
practicable. Except as set forth in Schedule 2.1 attached hereto, the Company
agrees not to file any other registration statement on Form S-3 until the
Registration Statement to be filed by the Company for the benefit of the Selling
Shareholder becomes effective. If the Company should breach this obligation,
then the Selling Shareholder shall have the remedies provided for in Article X.

         Section 2.2.      UNDERWRITTEN OFFERING. If any offering pursuant
to a Registration Statement pursuant to Section 2.1 hereof involves an
underwritten offering, the Selling Shareholder shall have the right to select
one legal counsel and the right to select the investment banker or bankers and
manager or managers to administer the offering (subject to the approval of the
Company, which approval shall not be unreasonably withheld, conditioned or
delayed). In the event that the Selling Shareholder elects not to participate in
such underwritten offering, the Registration Statement covering all of the
Registrable Securities shall contain appropriate plans of distribution
reasonably satisfactory to the Selling Shareholder.

         Section 2.3.      ELIGIBILITY FOR FORM S-3. The Company represents and
warrants that, to the best of its knowledge, it meets the registrant eligibility
and transaction requirements for the use of Form S-3 for registration of the
sale by the Selling Shareholder and the Company shall file all reports required
to be filed by the Company with the SEC in a timely manner so as to maintain
such eligibility for the use of Form S-3.

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                                  ARTICLE III.
                           OBLIGATIONS OF THE COMPANY

         In connection with the registration of the Registrable Securities, the
Company shall have the following obligations:

         Section 3.1.      The Company shall prepare promptly, and file with the
SEC as soon as practicable after the Closing (but in no event later than the
Filing Date), a Registration Statement with respect to the number of Registrable
Securities provided in Section 2.1, and thereafter use its commercially
reasonable efforts to cause such Registration Statement relating to Registrable
Securities to become effective as soon as possible after such filing, and keep
the Registration Statement effective pursuant to Rule 415 at all times until
such date as is the earlier of (i) the date on which all of the Registrable
Securities have been sold and (ii) the date on which the Registrable Securities
(in the opinion of Company's counsel) may be immediately sold to the public
without registration or restriction (including without limitation as to volume
by each holder thereof) under the 1933 Act (the "REGISTRATION PERIOD"), which
Registration Statement (including any amendments or supplements thereto and
prospectuses contained therein) shall not contain any untrue statement of a
material fact or omit to state a material fact required to be stated therein, or
necessary to make the statements therein not misleading.

         Section 3.2.      The Company shall prepare and file with the SEC such
amendments (including post-effective amendments) and supplements to the
Registration Statements and the prospectus used in connection with the
Registration Statements as may be necessary to keep the Registration Statements
effective at all times during the Registration Period, and, during such period,
comply with the provisions of the 1933 Act with respect to the disposition of
all Registrable Securities of the Company covered by the Registration
Statements, including any amendments that may be required to allow the permitted
assignees of Seller (as set forth in Section 10.6) to sell Registrable
Securities under the Registration Statements.

         Section 3.3.      The Company shall furnish to each Selling Shareholder
whose Registrable Securities are included in a Registration Statement and its
legal counsel (i) promptly after the same is prepared and publicly distributed,
filed with the SEC, or received by the Company, one copy of each Registration
Statement and any amendment thereto, each preliminary prospectus and prospectus
and each amendment or supplement thereto, and (ii) such number of copies of a
prospectus, including a preliminary prospectus, and all amendments and
supplements thereto and such other documents as such Selling Shareholder may
reasonably request in order to facilitate the disposition of the Registrable
Securities owned by such Selling Shareholder. The Company will immediately
notify each Selling Shareholder of the effectiveness of each Registration
Statement or any post-effective amendment. The Company will promptly respond to
any and all comments received from the SEC, with a view towards causing each
Registration Statement or any amendment thereto to be declared effective by the
SEC as soon as practicable and shall file an acceleration request as soon as
practicable following the resolution or clearance of all SEC comments or, if
applicable, following notification by the SEC that any such Registration
Statement or any amendment thereto will not be subject to review.

         Section 3.4.      The Company shall use reasonable efforts to (i)
register and qualify the Registrable Securities covered by the Registration
Statements under such other securities or

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"BLUE SKY" laws of such jurisdictions in the United States as each Selling
Shareholder may reasonably request, if an exemption from such securities or blue
sky laws is not otherwise available, (ii) prepare and file in those
jurisdictions such amendments (including post-effective amendments) and
supplements to such registrations and qualifications as may be necessary to
maintain the effectiveness thereof during the Registration Period, (iii) take
such other actions as may be necessary to maintain such registrations and
qualifications in effect at all times during the Registration Period, and (iv)
take all other actions reasonably necessary or advisable to qualify the
Registrable Securities for sale in such jurisdictions; provided, however, that
the Company shall not be required in connection therewith or as a condition
thereto to (a) qualify to do business in any jurisdiction where it would not
otherwise be required to qualify but for this Section 3.4, (b) subject itself to
general taxation in any such jurisdiction, (c) file a general consent to service
of process in any such jurisdiction, or (d) make any change in its charter or
bylaws, which in each case the Board of Directors of the Company determines to
be contrary to the best interests of the Company and its shareholders.

         Section 3.5.      In the event the Selling Shareholder selects
underwriters for the offering, the Company shall enter into and perform its
obligations under an underwriting agreement, in usual and customary form,
including, without limitation, customary indemnification and contribution
obligations, with the underwriters of such offering.

         Section 3.6.      As promptly as practicable after becoming aware of
such event, the Company shall notify each Selling Shareholder of the happening
of any event, of which the Company has knowledge, as a result of which the
prospectus included in any Registration Statement, as then in effect, includes
an untrue statement of a material fact or omission to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and use its commercially reasonable efforts promptly to prepare a
supplement or amendment to any Registration Statement to correct such untrue
statement or omission, and deliver such number of copies of such supplement or
amendment to each Selling Shareholder as such Selling Shareholder may reasonably
request; provided that, for not more than fifteen (15) consecutive trading days
(or a total of not more than thirty (30) trading days in any twelve (30) month
period), the Company may delay the disclosure of material non-public information
concerning the Company (as well as prospectus or Registration Statement
updating) the disclosure of which at the time is not, in the good faith opinion
of the Company, in the best interests of the Company (an "ALLOWED DELAY");
provided, further, that the Company shall promptly (i) notify the Selling
Shareholder in writing of the existence of (but in no event, without the prior
written consent of an Selling Shareholder, shall the Company disclose to such
Selling Shareholder any of the facts or circumstances regarding) material
non-public information giving rise to an Allowed Delay and (ii) advise the
Selling Shareholder in writing to cease all sales under such Registration
Statement until the end of the Allowed Delay. Upon expiration of the Allowed
Delay, the Company shall again be bound by the first sentence of this Section
3.6 with respect to the information giving rise thereto.

         Section 3.7.      The Company shall use its commercially reasonable
efforts to prevent the issuance of any stop order or other suspension of
effectiveness of any Registration Statement, and, if such an order is issued, to
obtain the withdrawal of such order at the earliest possible moment and to
notify each Selling Shareholder who holds Registrable Securities being sold (or,

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in the event of an underwritten offering, the managing underwriters) of the
issuance of such order and the resolution thereof.

         Section 3.8.      The Company shall permit a single firm of counsel
designated by the Selling Shareholder to review such Registration Statement, and
all amendments and supplements thereto (as well as all requests for acceleration
or effectiveness thereof (collectively, the "REGISTRATION DOCUMENTS")) a
reasonable period of time prior to their filing with the SEC, and not file (or
send) any Registration Documents in a form to which such counsel reasonably
objects and will not request acceleration of such Registration Statement without
prior notice to such counsel. The sections of such Registration Statement
covering information with respect to the Selling Shareholder, the Selling
Shareholder's beneficial ownership of securities of the Company or the Selling
Shareholder's intended method of disposition of Registrable Securities shall
conform to the information provided to the Company by the Selling Shareholder.

         Section 3.9.      The Company shall (i) cause all the Registrable
Securities covered by the Registration Statement to be listed on each national
securities exchange on which securities of the same class or series issued by
the Company are then listed, if any, if the listing of such Registrable
Securities is then permitted under the rules of such exchange, or (ii) to the
extent the securities of the same class or series are not then listed or
permitted to be listed on a national securities exchange, secure the designation
and quotation of all the Registrable Securities covered by the Registration
Statement on Nasdaq or, if not eligible for Nasdaq on the Nasdaq SmallCap.

         Section 3.10.     The Company shall provide a transfer agent and
registrar, which may be a single entity, for the Registrable Securities not
later than the effective date of the Registration Statement.

         Section 3.11.     At the request of the Selling Shareholder, the
Company shall prepare and file with the SEC such amendments (including
post-effective amendments) and supplements to a Registration Statement and any
prospectus used in connection with the Registration Statement as may be
necessary in order to change the plan of distribution set forth in such
Registration Statement.

         Section 3.12.     The Company shall not, and shall not agree to, allow
the holders of any securities of the Company to include any of their securities
in any Registration Statement under Section 2.1 hereof or any amendment or
supplement thereto under Section 3.2 hereof without the consent of the Selling
Shareholder. In addition, the Company shall not offer any securities for its own
account or the account of others in any Registration Statement under Section 2.1
hereof or any amendment or supplement thereto under Section 3.2 hereof without
the consent of the Selling Shareholder.

         Section 3.13.     The Company shall take all other reasonable actions
necessary to expedite and facilitate disposition by the Selling Shareholder of
Registrable Securities pursuant to a Registration Statement.

         Section 3.14.     The Company shall comply with all applicable laws
related to a Registration Statement and offering and sale of securities and all
applicable rules and regulations

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of governmental authorities in connection therewith (including without
limitation the 1933 Act and the 1934 Act (as defined below) and the rules and
regulations promulgated by the SEC).

                                  ARTICLE IV.
                     OBLIGATIONS OF THE SELLING SHAREHOLDER

         In connection with the registration of the Registrable Securities, the
Selling Shareholder shall have the following obligations:

         Section 4.1.      It shall be a condition precedent to the obligations
of the Company to complete the registration pursuant to this Agreement with
respect to the Registrable Securities of a particular Selling Shareholder that
such Selling Shareholder shall furnish to the Company such information regarding
itself, the Registrable Securities held by it and the intended method of
disposition of the Registrable Securities held by it as shall be reasonably
required to effect the registration of such Registrable Securities and shall
execute such documents in connection with such registration as the Company may
reasonably request. At least ten (10) days prior to the first anticipated filing
date of the Registration Statement, the Company shall notify each Selling
Shareholder of the information the Company requires from each such Selling
Shareholder.

         Section 4.2.      Each Selling Shareholder, by such Selling
Shareholder's acceptance of the Registrable Securities, agrees to cooperate with
the Company as reasonably requested by the Company in connection with the
preparation and filing of the Registration Statements hereunder, unless such
Selling Shareholder has notified the Company in writing of such Selling
Shareholder's election to exclude all of such Selling Shareholder's Registrable
Securities from the Registration Statements.

         Section 4.3.      If the services of an underwriter are engaged, each
Selling Shareholder agrees to enter into and perform such Selling Shareholder's
obligations under an underwriting agreement, in usual and customary form,
including, without limitation, customary indemnification and contribution
obligations, with the managing underwriter of such offering and take such other
actions as are reasonably required in order to expedite or facilitate the
disposition of the Registrable Securities, unless such Selling Shareholder has
notified the Company in writing of such Selling Shareholder's election to
exclude all of such Selling Shareholder's Registrable Securities from such
Registration Statement.

         Section 4.4.      Each Selling Shareholder agrees that, upon receipt of
any notice from the Company of the happening of any event of the kind described
in Section 3.6 or 3.7, such Selling Shareholder will immediately discontinue
disposition of Registrable Securities pursuant to the Registration Statement
covering such Registrable Securities until such Selling Shareholder's receipt of
the copies of the supplemented or amended prospectus contemplated by Section 3.6
or 3.7 and, if so directed by the Company, such Selling Shareholder shall
deliver to the Company or destroy all copies in such Selling Shareholder's
possession, of the prospectus covering such Registrable Securities current at
the time of receipt of such notice.

         Section 4.5.      No Selling Shareholder may participate in any
underwritten registration hereunder unless such Selling Shareholder (i) agrees
to sell such Selling Shareholder's Registrable Securities on the basis provided
in any underwriting arrangements in usual and

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customary form entered into by the Company, (ii) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents reasonably required under the terms of such underwriting
arrangements, and (iii) agrees to pay its pro rata share of all underwriting
discounts and commissions and any expenses in excess of those payable by the
Company pursuant to Section 5 below.

         Section 4.6.      The Selling Shareholder shall comply with all
applicable laws related to a Registration Statement and offering and sale of
securities and all applicable rules and regulations of governmental authorities
in connection therewith (including without limitation the 1933 Act and the 1934
Act (as defined below) and the rules and regulations promulgated by the SEC).

                                    ARTICLE V.
                            EXPENSES OF REGISTRATION

         All reasonable expenses, other than underwriting discounts and
commissions, incurred in connection with registrations, filings or
qualifications pursuant to Sections 2 and 3, including, without limitation, all
registration, listing and qualification fees, printers and accounting fees, the
fees and disbursements of legal counsel for the Company, and the reasonable fees
and disbursements of one legal counsel for all holders of Registrable
Securities, selected by the Selling Shareholder pursuant to Sections 2.2 and 3.8
hereof, shall be borne by the Company.

                                  ARTICLE VI.
                               INDEMNIFICATION

         In the event any Registrable Securities are included in a Registration
Statement under this Agreement:

         Section 6.1.      To the extent permitted by law, the Company will
indemnify, hold harmless and defend (i) each Selling Shareholder who holds such
Registrable Securities, (ii) the directors, officers, partners, employees,
agents and each person who controls any Selling Shareholder within the meaning
of the 1933 Act or the Securities Exchange Act of 1934, as amended (the "1934
ACT"), if any, (iii) any underwriter (as defined in the 1933 Act) for the
Selling Shareholder, and (iv) the directors, officers, partners, employees and
each person who controls any such underwriter within the meaning of the 1933 Act
or the 1934 Act, if any (each, an "INDEMNIFIED PERSON"), against any joint or
several losses, claims, damages, liabilities or expenses (collectively, together
with actions, proceedings or inquiries by any regulatory or self-regulatory
organization, whether commenced or threatened, in respect thereof, "CLAIMS") to
which any of them may become subject insofar as such Claims arise out of or are
based upon: (i) any untrue statement or alleged untrue statement of a material
fact in a Registration Statement or the omission or alleged omission to state
therein a material fact required to be stated or necessary to make the
statements therein not misleading; (ii) any untrue statement or alleged untrue
statement of a material fact contained in any preliminary prospectus if used
prior to the effective date of such Registration Statement, or contained in the
final prospectus (as amended or supplemented, if the Company files any amendment
thereof or supplement thereto with the SEC) or the omission or alleged omission
to state therein any material fact necessary to make the statements made
therein, in light of the circumstances under which the statements therein were

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made, not misleading; or (iii) any violation or alleged violation by the Company
of the 1933 Act, the 1934 Act, any other law, including, without limitation, any
state securities law, or any rule or regulation thereunder relating to the offer
or sale of the Registrable Securities (the matters in the foregoing clauses (i)
through (iii) being, collectively, "VIOLATIONS"). Subject to the restrictions
set forth in Section 6.3 with respect to the number of legal counsel, the
Company shall reimburse the Indemnified Person, promptly as such expenses are
incurred and are due and payable, for any reasonable legal fees or other
reasonable expenses incurred by them in connection with investigating or
defending any such Claim. Notwithstanding anything to the contrary contained
herein, the indemnification agreement contained in this Section 6.1: (i) shall
not apply to a Claim arising out of or based upon a Violation which occurs in
reliance upon and in conformity with information furnished in writing to the
Company by any Indemnified Person or underwriter for such Indemnified Person
expressly for use in connection with the preparation of such Registration
Statement or any such amendment thereof or supplement thereto; (ii) shall not
apply to amounts paid in settlement of any Claim if such settlement is effected
without the prior written consent of the Company, which consent shall not be
unreasonably withheld; (iii) with respect to any preliminary prospectus, shall
not inure to the benefit of any Indemnified Person if the untrue statement or
omission of material fact contained in the preliminary prospectus was corrected
on a timely basis in the prospectus, as then amended or supplemented, such
corrected prospectus was timely made available by the Company pursuant to
Section 3.3 hereof, and the Indemnified Person was promptly advised in writing
not to use the incorrect prospectus prior to the use giving rise to a Violation
and such Indemnified Person, notwithstanding such advice, used it; and (iv)
shall not apply to any offers to sell or sales made by an Indemnified Person
after receipt of the notice referred to in Section 3.6, clause (ii) and during
the period of the Allowed Delay. Such indemnity shall remain in full force and
effect regardless of any investigation made by or on behalf of the Indemnified
Person and shall survive the transfer of the Registrable Securities by the
Selling Shareholder pursuant to Section 9.

         Section 6.2.      In connection with any Registration Statement in
which an Selling Shareholder is participating, each such Selling Shareholder
agrees severally and not jointly to indemnify, hold harmless and defend, to the
same extent and in the same manner set forth in Section 6.1, the Company, each
of its directors, each of its officers who signs the Registration Statement,
each person, if any, who controls the Company within the meaning of the 1933 Act
or the 1934 Act, any underwriter and any other shareholder selling securities
pursuant to the Registration Statement or any of its directors or officers or
any person who controls such shareholder or underwriter within the meaning of
the 1933 Act or the 1934 Act (collectively and together with an Indemnified
Person, an "INDEMNIFIED PARTY"), against any Claim to which any of them may
become subject, under the 1933 Act, the 1934 Act or otherwise, insofar as such
Claim arises out of or is based upon (i) any Violation, in each case to the
extent (and only to the extent) that such Violation occurs in reliance upon and
in conformity with written information furnished to the Company by such Selling
Shareholder expressly for use in connection with such Registration Statement or
(ii) any offers to sell or sales by such Selling Shareholder after receipt by
such Selling Shareholder of the notice referred to in Section 3.6, clause (ii)
and during the period of the Allowed Delay; and subject to Section 6.3, such
Selling Shareholder will reimburse any legal or other expenses (promptly as such
expenses are incurred and are due and payable) reasonably incurred by them in
connection with investigating or defending any such Claim; provided, however,
that the indemnity agreement contained in this Section 6.2 shall not apply to
amounts paid in settlement of any Claim if such settlement is effected without
the prior written

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consent of such Selling Shareholder, which consent shall not be unreasonably
withheld; provided, further, however, that the Selling Shareholder shall be
liable under this Agreement (including this Section 6.2 and Section 7) for only
that amount as does not exceed the net proceeds to such Selling Shareholder as a
result of the sale of Registrable Securities pursuant to such Registration
Statement. Such indemnity shall remain in full force and effect regardless of
any investigation made by or on behalf of such Indemnified Party and shall
survive the transfer of the Registrable Securities by the Selling Shareholder
pursuant to Section 9. Notwithstanding anything to the contrary contained
herein, the indemnification agreement contained in this Section 6.2 with respect
to any preliminary prospectus shall not inure to the benefit of any Indemnified
Party if the untrue statement or omission of material fact contained in the
preliminary prospectus was corrected on a timely basis in the prospectus, as
then amended or supplemented, and the Indemnified Party was promptly advised in
writing not to use the incorrect information prior to the use giving rise to a
Violation and such Indemnified Party, notwithstanding such advice, used it.

         Section 6.3.      Promptly after receipt by an Indemnified Party under
this Section 6 of notice of the commencement of any action (including any
governmental action), such Indemnified Party shall, if a Claim in respect
thereof is to be made against any indemnifying party under this Section 6,
deliver to the indemnifying party a written notice of the commencement thereof,
and the indemnifying party shall have the right to participate in, and, to the
extent the indemnifying party so desires, jointly with any other indemnifying
party similarly noticed, to assume control of the defense thereof with counsel
selected by the indemnifying party and reasonably satisfactory to the
Indemnified Party, as the case may be; provided, however, that an Indemnified
Party shall have the right to retain its own counsel with the fees and expenses
to be paid by the indemnifying party, if, in the reasonable opinion of counsel
retained by the indemnifying party, the representation by such counsel of the
Indemnified Party and the indemnifying party would be inappropriate due to
actual or potential differing interests between such Indemnified Party and any
other party represented by such counsel in such proceeding. The indemnifying
party shall pay for only one separate legal counsel for the Indemnified Persons
or the Indemnified Parties, as applicable, and such legal counsel shall be
selected by the Selling Shareholder, if the Selling Shareholder is entitled to
indemnification hereunder, or the Company, if the Company is entitled to
indemnification hereunder, as applicable. The failure to deliver written notice
to the indemnifying party within a reasonable time of the commencement of any
such action shall not relieve such indemnifying party of any liability to the
Indemnified Party under this Section 6, except to the extent that the
indemnifying party is actually prejudiced in its ability to defend such action.
The indemnification required by this Section 6 shall be made by periodic
payments of the amount thereof during the course of the investigation or
defense, as such expense, loss, damage or liability is incurred and is due and
payable.

                                  ARTICLE VII.
                                  CONTRIBUTION

         To the extent any indemnification by an indemnifying party is
prohibited or limited by law, the indemnifying party agrees to make the maximum
contribution with respect to any amounts for which it would otherwise be liable
under Section 6 to the fullest extent permitted by law; provided, however, that
(i) no contribution shall be made under circumstances where the indemnifying
party would not have been liable for indemnification under the fault standards
set

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forth in Section 6, (ii) no seller of Registrable Securities guilty of
fraudulent misrepresentation (within the meaning of Section 11(f) of the 1933
Act) shall be entitled to contribution from any seller of Registrable Securities
who was not guilty of such fraudulent misrepresentation, and (iii) contribution
(together with any indemnification or other obligations under this Agreement) by
any seller of Registrable Securities shall be limited in amount to the net
amount of proceeds received by such seller from the sale of such Registrable
Securities.

                                 ARTICLE VIII.
                           REPORTS UNDER THE 1934 ACT

         With a view to making available to the Selling Shareholder the benefits
of Rule 144 promulgated under the 1933 Act or any other similar rule or
regulation of the SEC that may at any time permit the Selling Shareholder to
sell securities of the Company to the public without registration ("RULE 144"),
the Company agrees to:

                  (a)      make and keep public information available, as those
         terms are understood and defined in Rule 144;

                  (b)      file with the SEC in a timely manner all reports and
         other documents required of the Company under the 1933 Act and the 1934
         Act so long as the Company remains subject to such requirements and the
         filing of such reports and other documents is required for the
         applicable provisions of Rule 144; and

                  (c)      furnish to each Selling Shareholder so long as such
         Selling Shareholder owns Registrable Securities, promptly upon request,
         such information as may be reasonably requested to permit such Selling
         Shareholder to sell such securities pursuant to Rule 144 without
         registration.

                                  ARTICLE IX.
                        AMENDMENT OF REGISTRATION RIGHTS

         Provisions of this Agreement may be amended and the observance thereof
may be waived (either generally or in a particular instance and either
retroactively or prospectively), only with written consent of the Company and
the Selling Shareholder.

                                   ARTICLE X.
                                    REMEDIES

         In the event the Company fails to file with the SEC a Registration
Statement with respect to all of the Registrable Securities on or before the
Filing Date, and such failure is not due to any breach of its obligations by the
Selling Shareholder hereunder or any delay caused by the Selling Shareholder,
the Selling Shareholder shall have the following alternative (and not
cumulative) remedies: (i) if such Registration Statement is not filed within
thirty (30) days following the Filing Date, the Selling Shareholder shall have
an option (the "Put Option") pursuant to which the Selling Shareholder may by
written demand upon the Company require the Company to purchase from the Selling
Shareholder all of the Registrable Securities for a purchase price equal to a
total of One Million Four Hundred Fifty Thousand Dollars ($1,450,000), plus
interest at the

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rate of ten percent (10%) per annum on the unpaid balance of the purchase price,
which interest shall begin to accrue on the unpaid balance of the purchase price
fifteen (15) days after the Company receives written demand for such purchase
from the Selling Shareholder, and the Closing on the purchase and sale of the
Registrable Securities pursuant to the exercise of such Put Option shall occur
not later than fifteen (15) days following the date of exercise of such option;
(ii) obtain from the Company in immediately available funds an amount equal to
the total damages suffered by Selling Shareholder as a result of the failure to
timely file such Registration Statement, including litigation costs and
reasonable attorneys fees incurred by Selling Shareholder in obtaining such
remedy; or (iii) specific performance of this Agreement against the Company and
require the Company to fully perform all of its obligations under this
Agreement.

                                   ARTICLE XI.
                                  MISCELLANEOUS

         Section 11.1.     A person or entity is deemed to be a holder of
Registrable Securities whenever such person or entity owns of record such
Registrable Securities. If the Company receives conflicting instructions,
notices or elections from two or more persons or entities with respect to the
same Registrable Securities, the Company shall act upon the basis of
instructions, notice or election received from the registered owner of such
Registrable Securities.

         Section 11.2.     Any notices required or permitted to be given under
the terms hereof shall be given in the manner sent by certified or registered
mail (return receipt requested) or delivered personally or by courier (including
a recognized overnight delivery service) or by facsimile and shall be effective
five (5) calendar days after being placed in the mail, if mailed by regular
United States mail, or upon receipt, if delivered personally or by courier
(including a recognized overnight delivery service) or by facsimile, in each
case addressed to a party. The addresses and facsimile numbers for such
communications shall be:

                           If to the Company:

                           Zix Corporation
                           2711 North Haskell Avenue
                           Suite 2300 LB36
                           Dallas, Texas 75246
                           Attention: General Counsel
                           Facsimile: (214) 515-7538

If to Selling Shareholder, to the address and facsimile number set forth in the
Asset Purchase Agreement with a copy to the counsel specified in the Asset
Purchase Agreement or (in the case of permitted assigns, below the Selling
Shareholder's signature on the signature page to this Agreement).

         Section 11.3.     Failure of any party to exercise any right or remedy
under this Agreement or otherwise, or delay by a party in exercising such right
or remedy, shall not operate as a waiver thereof.

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<PAGE>

         Section 11.4.     GOVERNING LAW. THIS AGREEMENT WILL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS WITHOUT REFERENCE TO
THE PRINCIPLES OF CONFLICT OF LAWS OR ANY OTHER PRINCIPLE THAT COULD RESULT IN
THE APPLICATION OF THE LAWS OF ANY OTHER JURISDICTION.

         Section 11.5.     This Agreement and the Asset Purchase Agreement
(including all schedules and exhibits thereto) constitute the entire agreement
among the parties hereto with respect to the subject matter hereof and thereof.
There are no restrictions, promises, warranties or undertakings, other than
those set forth or referred to herein and therein. This Agreement and the Asset
Purchase Agreement supersede all prior agreements and understandings among the
parties hereto with respect to the subject matter hereof and thereof.

         Section 11.6.     The Selling Shareholder may assign its rights
hereunder to the current shareholders of the Selling Shareholder that execute a
joinder page indicating their agreement to be bound to the terms and conditions
of this Agreement. This Agreement shall inure to the benefit of and be binding
upon the successors and assigns of each of the parties hereto.

         Section 11.7.     The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

         Section 11.8.     This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original but all of which shall
constitute one and the same agreement. This Agreement, once executed by a party,
may be delivered to the other party hereto by facsimile transmission of a copy
of this Agreement bearing the signature of the party so delivering this
Agreement.

         Section 11.9.     Each party shall do and perform, or cause to be done
and performed, all such further acts and things, and shall execute and deliver
all such other agreements, certificates, instruments and documents, as the other
party may reasonably request in order to carry out the intent and accomplish the
purposes of this Agreement and the consummation of the transactions contemplated
hereby.

         Section 11.10.    The language used in this Agreement will be deemed to
be the language chosen by the parties to express their mutual intent, and no
rules of strict construction will be applied against any party.

         Section 11.11.    In the event that any provision of this Agreement is
invalid or unenforceable under any applicable statute or rule of law, then such
provision shall be deemed inoperative to the extent that it may conflict
therewith and shall be deemed modified to conform with such statute or rule of
law. Any provision hereof which may prove invalid or unenforceable under any law
shall not affect the validity or enforceability of any other provision hereof.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                       12

<PAGE>

         IN WITNESS WHEREOF, the Company and the Selling Shareholder have caused
this Agreement to be duly executed as of the date first above written.

                                            ZIX CORPORATION

                                            By:
                                                 Name:
                                                 Title:

                                            POCKETSCIPT L.L.C.

                                            By:
                                                 Name:
                                                 Title:

                                       13

<PAGE>

                                     JOINDER

         The undersigned, who represents that it is a member of PocketScript
L.L.C., hereby executes this signature page to that certain Registration Rights
Agreement (the "Registration Rights Agreement"), dated July 22, 2003, between
PocketScript L.L.C. and Zix Corporation, thereby indicating the undersigned's
agreement to the terms and conditions of the Registration Rights Agreement, as
fully and effectively as if the undersigned had executed and delivered this page
at the time originally executed by each of Pocket Script L.L.C. and Zix
Corporation.

                                           _______________________________
                                           Name: _________________________
                                           Date: _________________________

                                           Address: _____________________
                                           _____________________
                                           _____________________

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