Document:

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                                                                     EXHIBIT 4.8

                               SECURITY AGREEMENT

     THIS SECURITY AGREEMENT is dated as of September 17, 2002 between ZIX
CORPORATION, a Texas corporation with its headquarters located at 2711 N.
Haskell Avenue, Suite 2300, LB36, Dallas Texas, 75204 ("DEBTOR"), and PROMETHEAN
ASSET MANAGEMENT L.L.C., a Delaware limited liability company, in its capacity
as collateral agent for the Funds identified below (in such capacity, the
"SECURED PARTY").

                                   WITNESSETH

     WHEREAS, Debtor has executed and delivered to each of the Funds those
certain secured convertible notes each made by Debtor and dated as of the date
hereof (as the same may be amended and in effect from time to time, individually
a "NOTE" and collectively the "NOTES"). The Notes were issued pursuant to a
certain Securities Purchase Agreement dated as of September 17, 2002 (as the
same has been and hereafter may be amended, modified, supplemented or restated,
the "SECURITIES PURCHASE AGREEMENT") by and among, inter alia, HFTP Investment
L.L.C., a Delaware limited liability company, Gaia Offshore Master Fund, LTD., a
Cayman Islands exempt company, and Caerus Fund Ltd., a Cayman Islands exempt
company (collectively, the "FUNDS"), and pursuant to which the Funds have made
loans to Debtor in the original aggregate principal amount of $8,000,000; and

     WHEREAS, it is a condition under the Notes and the Securities Purchase
Agreement that Debtor shall grant the security interests contemplated by this
Agreement to Secured Party as collateral agent on behalf of the Funds for
purposes of maintaining, administering, perfecting and enforcing such security
interests, in order to secure the payment and performance of Debtor's
indebtedness and obligations under the Notes;

     NOW, THEREFORE, in consideration of the premises and in order to induce the
Funds to purchase the Notes and enter into the Securities Purchase Agreement,
and for other good and valuable consideration, Debtor hereby agrees with Secured
Party, for its benefit and the benefit of the Funds, as follows:

SECTION 1. Definitions

     1.1 Certain Defined Terms. Terms defined in the Notes and not otherwise
defined herein shall have the respective meanings provided for in the Notes or,
to the extent not defined therein, in the Securities Purchase Agreement. The
following terms shall have the respective meanings provided for in the UCC (as
defined below): "ACCOUNTS", "ACCOUNT DEBTOR", "BUYER IN ORDINARY COURSE OF
BUSINESS", "CHATTEL PAPER", "COMMERCIAL TORT CLAIM", "DEPOSIT ACCOUNT",
"DOCUMENTS", "ELECTRONIC CHATTEL PAPER", "EQUIPMENT", "GENERAL INTANGIBLES",
"GOODS", "INSTRUMENTS", "INVENTORY", "INVESTMENT PROPERTY", "LETTER OF CREDIT",
"LETTER-OF-CREDIT RIGHTS", "LICENSEE IN ORDINARY COURSE OF BUSINESS",
"PROCEEDS", "RECORD", "SOFTWARE", "SUPPORTING OBLIGATIONS", "SECURITIES
ACCOUNT", "SECURITY ENTITLEMENT" and

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"TANGIBLE CHATTEL PAPER". The following terms, as used herein, have the meanings
set forth below:

     "COLLATERAL" has the meaning assigned to that term in Section 2.

     "CONTROL" means the manner in which "control" is achieved under the UCC
with respect to a particular item of Collateral.

     "EXCLUDED ACCOUNT" means Account # [omitted] at Bank of America Merchants
Services, Inc., A Bank of America Company, in the name of ZixMail.com, Inc.;
provided that the balance in such account at no time exceeds $300,000.

     "EXCLUDED ASSETS" means Debtor's interest in Maptuit Corporation, an
Ontario corporation, and CStone Consulting, Inc., a California corporation, as
such interests exist on the date of this Agreement, and any securities issued in
exchange therefore or replacement thereof (provided that no additional
consideration is paid by Debtor in connection with such exchange or
replacement).

     "INTELLECTUAL PROPERTY" means collectively all of the following: Patents
and Trademarks.

     "LOAN DOCUMENT" means, collectively, this Agreement, the Notes, the
Securities Purchase Agreement and any subordination agreement entered into
pursuant to the requirements of the Notes or Securities Purchase Agreement.

     "OBLIGATIONS" means all obligations, liabilities and indebtedness of every
nature of Debtor from time to time owed to Secured Party and/or any Fund under
the Notes, including the principal amount of all debts, claims and indebtedness,
accrued and unpaid interest and all fees, costs and expenses whether primary,
secondary, direct, contingent, fixed or otherwise, heretofore, now and/or from
time to time hereafter owing due or payable whether before or after the filing
of a proceeding under the Bankruptcy Law by or against Debtor.

     "PATENTS" means collectively all of the following: (a) all patents and
patent applications and the inventions and improvements described and claimed
therein, and patentable inventions; (b) the reissues, divisions, continuations,
renewals, extensions and continuations-in-part of any of the foregoing; (c) all
income, royalties, damages and payments now or hereafter due and/or payable
under any of the foregoing or with respect to any of the foregoing, including,
without limitation, damages and payments for past, present and future
infringements of any of the foregoing; (d) the right to sue for past, present
and future infringements of any of the foregoing; and (e) all rights
corresponding to any of the foregoing throughout the world.

     "PLEDGED ACCOUNTS" has the meaning assigned to that term in Section 7.

     "SECURED OBLIGATIONS" has the meaning assigned to that term in Section 3.

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     "SECURITY INTERESTS" means the security interests granted or provided for
hereunder.

     "TRADEMARKS" means collectively all of the following: (a) all trademarks,
trade names, corporate names, company names, business names, fictitious business
names, trade styles, service marks, logos, other business identifiers, prints
and labels on which any of the foregoing have appeared or appear, all
registrations and recordings thereof, and all applications in connection
therewith; (b) all renewals thereof; (c) all income, royalties, damages and
payments now or hereafter due and/or payable under any of the foregoing or with
respect to any of the foregoing including damages and payments for past, present
and future infringements of any of the foregoing; (d) the right to sue for past,
present and future infringements of any of the foregoing; (e) all rights
corresponding to any of the foregoing throughout the world; and (f) all goodwill
associated with and symbolized by any of the foregoing.

     "UCC" means the Uniform Commercial Code as in effect from time to time in
the State of New York.

     1.2 Other Definition Provisions. References to "Sections," "subsections"
and "Schedules" shall be to Sections, subsections and Schedules, respectively,
of this Agreement unless otherwise specifically provided. For purposes hereof,
"including" is not limiting and "or" is not exclusive. Any of the terms defined
in subsection 1.1 may, unless the context otherwise requires, be used in the
singular or the plural depending on the reference. All references to statutes
and related regulations shall include (unless otherwise specifically provided
herein) any amendments of same and any successor statutes and regulations.

SECTION 2. Grant of Security Interests; Agreement to Release

     To secure the payment, performance and observance of the Secured
Obligations, Debtor hereby assigns, pledges, hypothecates, delivers, sets over
and transfers to Secured Party and grants to Secured Party, for the benefit of
the Funds, a continuing security interest in, right of setoff against, and an
assignment to Secured Party of all of Debtor's personal property and rights to
personal property, in each case, whether now owned or existing or hereafter
acquired or arising and regardless of where located and shall include the
following (all being collectively referred to herein as the "COLLATERAL;"
provided, however, that in no event shall the Collateral include the Excluded
Account or the Excluded Assets):

          (a)  Accounts;

          (b)  Chattel Paper;

          (c)  Commercial Tort Claims;

          (d)  Deposit Accounts and Securities Accounts, all cash, and other
               property deposited therein from time to time and other monies and
               property in the possession or under the control of Secured Party
               or any affiliate, representative, agent or correspondent of
               Secured Party;

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          (e)  Documents;

          (f)  Equipment;

          (g)  General Intangibles;

          (h)  Goods;

          (i)  Instruments;

          (j)  Inventory;

          (k)  Investment Property and Securities Entitlements;

          (l)  Letter-of-Credit Rights;

          (m)  Supporting Obligations;

          (n)  All other personal property whether or not subject to the UCC;

          (o)  All other financial assets of Debtor, whether or not subject to
               the UCC;

          (p)  All books, records, ledger cards, files, correspondence, computer
               programs, tapes, disks and related data processing Software that
               at any time evidence or contain information relating to any of
               the property described in subparts (a) - (o) above or are
               otherwise necessary or helpful in the collection thereof or
               realization thereon; and

          (q)  Proceeds and products of all or any of the property described in
               subparts (a) - (p) above.

Those items of Collateral described in clauses (d), (i), (k), (m) and (o) above
(and clauses (p) and (q) to the extent applicable thereto) constitute and are
hereinafter referred to as the "PRIMARY COLLATERAL". Those items of Collateral
not consisting of Primary Collateral are hereinafter referred to as the
"ADDITIONAL COLLATERAL".

     Secured Party hereby agrees to terminate and release all or any portion of
the liens and security interests granted hereunder in the Additional Collateral
within three (3) Business Days of receipt by Secured Party of written notice
from the Debtor requesting such termination and release and stating that in
Debtor's good faith reasonable determination the existence of the Secured
Party's lien on the Additional Collateral (or designated portion thereof) would
interfere materially with a substantive business transaction or relationship
currently being contemplated by Debtor.

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SECTION 3. Security for Obligations

     This Agreement secures the payment and performance of the Obligations and
all indebtedness, liabilities and obligations of Debtor now existing or
hereafter created or arising under this Agreement and all renewals, extensions,
restructurings and refinancings of any of the above including, without
limitation, (i) any additional indebtedness which may be extended to Debtor
pursuant to any restructuring or refinancing of Debtor's indebtedness under the
Notes, (ii) any fees, costs or expenses from time to time hereafter owing, due
or payable under this Agreement whether before or after the filing of a
proceeding under the Bankruptcy Law by or against Debtor, and (iii) any
post-petition interest accruing during any bankruptcy, reorganization or other
similar proceeding (all such indebtedness, liabilities and obligations of Debtor
being collectively referred to herein as the "SECURED OBLIGATIONS").

SECTION 4. Debtor Remains Liable

     Anything herein to the contrary notwithstanding: (a) Debtor shall remain
liable under the contracts and agreements included in the Collateral to the
extent set forth therein to perform all of its duties and obligations thereunder
to the same extent as if this Agreement had not been executed; (b) the exercise
by Secured Party of any of the rights hereunder shall not release Debtor from
any of its duties or obligations under the contracts and agreements included in
the Collateral; (c) neither Secured Party nor any Fund shall have any obligation
or liability under the contracts and agreements included in the Collateral by
reason of this Agreement, nor shall Secured Party or any Fund be obligated to
perform any of the obligations or duties of Debtor thereunder or to take any
action to collect or enforce any claim for payment assigned hereunder; and (d)
neither Secured Party nor any Fund shall have any liability in contract or tort
for Debtor's acts or omissions.

SECTION 5. Representations and Warranties

     In order to induce Secured Party to enter into this Agreement, Debtor
represents and warrants to Secured Party as follows:

     5.1 Binding Obligation. This Agreement is the legally valid and binding
obligation of Debtor, enforceable against it in accordance with its terms,
except as enforcement may be limited by bankruptcy, insolvency, reorganization,
moratorium, or similar laws or equitable principles relating to or limiting
creditor's rights generally.

     5.2 State of Organization. Debtor was organized and remains organized
solely under the laws of the State of Texas. Schedule I sets forth the Debtor's
organizational identification number or states that one does not exist.

     5.3 Location of Primary Collateral. There is no Primary Collateral other
than the accounts identified on Schedule I, except as otherwise specified on
Schedule I. Schedule I includes all Securities Accounts and Deposit Accounts
maintained by or on behalf of Debtor. All hereafter acquired Primary Collateral
will be either located at the address set forth in the

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preamble or at the places, or deposited in an account, identified on Schedule I,
except as otherwise permitted hereunder.

     5.4 Ownership of Collateral; Bailees. Debtor owns the Collateral and will
own all after-acquired Collateral. Except for the Security Interests, Debtor
owns the Primary Collateral, and will own all after-acquired Primary Collateral,
free and clear of any lien or security interest. No effective financing
statement or other form of lien notice covering all or any part of the
Collateral is on file in any recording office, except for those in favor of
Secured Party. None of the Primary Collateral is in the possession of any
consignee, bailee, warehouseman, agent or processor. No other Person has Control
of any of the Collateral.

     5.5 Office Locations; Fictitious Names. The mailing address, principal
place of business, chief executive office and office where Debtor keeps its
books and records relating to the Accounts, Chattel Paper, Documents, General
Intangibles, Instruments and Investment Property is located at the address set
forth in the preamble. Debtor has no other places of business except those
separately specified on Schedule I. Debtor does not do business and has not done
business during the past five years under any name, tradename or fictitious
business name except as disclosed on Schedule II.

     5.6 Perfection. Secured Party has a valid, perfected and first priority
security interest in the Primary Collateral, securing the payment of the Secured
Obligations, and such Security Interests are entitled to all of the rights,
priorities and benefits afforded by the UCC or other applicable law as enacted
in any relevant jurisdiction which relates to perfected security interests.

     5.7 Governmental Authorizations; Consents. No authorization, approval or
other action by, and no notice to or filing with, any domestic or foreign
governmental authority or regulatory body or consent of any other Person is
required for (a) the grant by Debtor of the Security Interests granted hereby or
for the execution, delivery or performance of this Agreement by Debtor; (b) the
perfection of the Security Interests granted hereby (except for filing UCC
financing statements with the appropriate jurisdiction and filing the Security
Agreement with the U.S. Patent and Trademark Office, as applicable); or (c) the
exercise by Secured Party of its rights and remedies hereunder (except as may
have been taken by or at the direction of Debtor or Secured Party).

     5.8 Accounts. To Debtor's knowledge, each existing Account constitutes, and
each hereafter arising Account will constitute, the legally valid and binding
obligation of the applicable Account Debtor.

     5.9 Chattel Paper. Debtor does not hold Chattel Paper in the ordinary
course of its business.

     5.10 Commercial Tort Claims. Debtor does not currently own any Commercial
Tort Claims.

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     5.11 Intellectual Property. To Debtor's knowledge, all Patents and
Trademarks owned by Debtor are valid, subsisting and enforceable and all filings
necessary to maintain the effectiveness of such registrations have been made.

     5.12 Inventory. All Inventory is not subject to any licensing, patent,
trademark, trade name or copyright agreement with any Person that restricts
Debtor's ability to manufacture and/or sell the Inventory.

     5.13 Accurate Information. All information heretofore, herein or hereafter
supplied to Secured Party by or on behalf of Debtor with respect to the
Collateral is and will be accurate and complete in all material respects.

SECTION 6. Further Assurances; Covenants

     6.1 Other Documents and Actions. Debtor will, from time to time, at its
expense, promptly execute and deliver all further instruments and documents and
take all further action that may be necessary or desirable, or that Secured
Party may request, in order to create, perfect and protect any Security
Interests or to enable Secured Party to exercise and enforce its rights and
remedies hereunder or under the Notes with respect to any Collateral. Without
limiting the generality of the foregoing, Debtor will: (a) execute and file such
financing or continuation statements, or amendments thereto, and such other
instruments, documents or notices, as may be necessary or desirable, or as
Secured Party may request, in order to create, perfect and protect the Security
Interests; (b) at any reasonable time, upon demand by Secured Party, exhibit the
Collateral to allow inspection of the Collateral by Secured Party or Persons
designated by Secured Party and to examine and make copies of the records of
Debtor related thereto, and to discuss the Collateral and the records of Debtor
with respect thereto with, and to be advised as to the same by, Debtor's
officers and employees and, after the occurrence and during the continuance of a
Triggering Event or an Event of Default, with any other Person which is or may
be obligated with respect to any Collateral; and (c) upon Secured Party's
request, appear in and defend any action or proceeding that may affect Debtor's
title to or Secured Party's security interest in the Collateral.

     6.2 Secured Party Authorized. Debtor hereby authorizes Secured Party to
file one or more financing or continuation statements, and amendments thereto
(or similar documents required by any laws of any applicable jurisdiction),
relating to all or any part of the Collateral without the signature of Debtor.

     6.3 Corporate or Name Change. Debtor will give Secured Party at least ten
(10) business days prior written notice of any change in Debtor's name,
identity, mailing address, jurisdiction of organization or corporate structure;
provided that such information is publicly disclosed prior to or simultaneously
with such notice. With respect to any such change, Debtor will promptly execute
and deliver such instruments, documents and notices and take such actions, as
Secured Party deems necessary or desirable to create, perfect and protect the
security interests of Secured Party in the Collateral.

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     6.4 Business Locations. Subject to the next sentence, Debtor will keep the
Primary Collateral (other than Collateral in the possession of Secured Party and
cash on deposit in permitted Deposit Accounts) at the locations specified in the
preamble or on Schedule I. Debtor will give Secured Party at least ten (10)
business days prior written notice of any change in Debtor's chief executive
office and principal place of business or of any new location of business or any
new location for any of the Collateral; provided that such information is
publicly disclosed prior to or simultaneously with such notice. With respect to
any new location (which in any event shall be within the continental United
States), Debtor will execute and deliver such instruments, documents and notices
and take such actions, as Secured Party deems necessary to create, perfect and
protect the security interests of Secured Party in the Collateral.

     6.5 Bailees. No Primary Collateral shall at any time be in the possession
or control of any bailee or any of Debtor's agents without Secured Party's prior
written consent and unless, if Secured Party has so requested, such bailee or
agent holds all such Primary Collateral for Secured Party's benefit.

     6.6 Instruments. Debtor will deliver to Secured Party all Instruments duly
endorsed and, if requested, accompanied by duly executed instruments of transfer
or assignment, all in form and substance satisfactory to Secured Party. Debtor
will also deliver to Secured Party all security agreements securing any
Instruments and execute UCC financing statement amendments assigning to Secured
Party any UCC financing statements filed by Debtor in connection with such
security agreements.

     6.7 Chattel Paper. Debtor will deliver to Secured Party all Tangible
Chattel Paper duly endorsed and, if requested, accompanied by duly executed
instruments of transfer or assignment, all in form and substance satisfactory to
Secured Party. Debtor will provide Secured Party with Control of all Electronic
Chattel Paper, if requested, by having Secured Party identified as the assignee
of the Records(s) pertaining to the single authoritative copy thereof and
otherwise complying with the applicable elements of Control set forth in the
UCC. Debtor will also, if requested, deliver to Secured Party all security
agreements securing any Chattel Paper and execute UCC financing statement
amendments assigning to Secured Party any UCC financing statements filed by
Debtor in connection with such security agreements. Debtor will mark
conspicuously all Chattel Paper with a legend, in form and substance
satisfactory to Secured Party, indicating that such Chattel Paper is subject to
the Security Interests.

     6.8 Letters of Credit. If requested, Debtor will deliver to Secured Party
all Letters of Credit duly endorsed and accompanied by duly executed instruments
of transfer or assignment, all in form and substance satisfactory to Secured
Party. If requested, Debtor will also deliver to Secured Party all security
agreements securing any Letters of Credit and execute UCC financing statement
amendments assigning to Secured Party any UCC financing statements filed by
Debtor in connection with such security agreements.

     6.9 Filing Requirements. None of the Collateral is of a type in which
security interests or liens may be registered, recorded or filed under, or
notice thereof given under, any federal statute or regulation (other than the
Company's Patents and Trademarks). Debtor shall

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promptly notify Secured Party in writing upon acquiring any interest hereafter
in Collateral that is of a type where a security interest or lien may be
registered, recorded of filed under, or notice thereof given under, any federal
statute or regulation.

     6.10 Investment Property. Debtor will take any and all actions necessary
(or required or requested by Secured Party), from time to time, to (a) cause
Secured Party to obtain exclusive Control of any Investment Property (including
Securities Accounts and Securities Entitlements) owned by Debtor in a manner
acceptable to Secured Party and (b) obtain from any issuers of Investment
Property and such other Persons, for the benefit of Secured Party, written
confirmation of Secured Party's Control over such Investment Property upon terms
and conditions acceptable to Secured Party. For purposes of this subsection
6.10, Secured Party shall have exclusive Control of Investment Property if (i)
such Investment Property consists of certificated securities and Debtor delivers
such certificated securities to Secured Party (with appropriate endorsements if
such certificated securities are in registered form); (ii) such Investment
Property consists of uncertificated securities and either (x) Debtor delivers
such uncertificated securities to Secured Party or (y) the issuer thereof
agrees, pursuant to documentation in form and substance satisfactory to Secured
Party, that it will comply with instructions originated by Secured Party without
further consent by Debtor; and (iii) such Investment Property consists of
security entitlements and either (x) Secured Party becomes the entitlement
holder thereof or (y) the appropriate securities intermediary agrees, pursuant
to documentation in form and substance satisfactory to Secured Party, that it
will comply with entitlement orders originated by Secured Party without further
consent by Debtor.

     6.11 Accounts. Except as otherwise provided in this subsection 6.11, Debtor
shall continue to collect, at its own expense, all amounts due or to become due
Debtor under the Accounts and apply such amounts as are so collected to the
outstanding balances thereof. Secured Party shall have the right at any time
after the occurrence and during the continuance of an Event of Default or a
Triggering Event to: (a) notify the Account Debtor under any Accounts (or any
other Person obligated thereon) of the assignment of such Accounts to Secured
Party and to direct such Account Debtors and other Persons to make payment of
all amounts due or to become due or otherwise render performance directly to
Secured Party; (b) exercise the rights of Debtor with respect to the obligation
of the Account Debtor to make payment or otherwise render performance to Debtor
and with respect to any property that secures the obligations of the Account
Debtor or any other Person obligated on the Collateral; and (c) adjust, settle
or compromise the amount or payment of such Accounts. After the occurrence and
during the continuance of an Event of Default or a Triggering Event (i) all
amounts and Proceeds received by Debtor with respect to the Accounts shall be
received in trust for the benefit of Secured Party shall be segregated from
other funds of Debtor and shall be forthwith paid over to Secured Party in the
same form as so received (with any necessary endorsement) to be held in the
Pledged Accounts pursuant to Section 7 or applied pursuant to Section 14.

     6.12 Commercial Tort Claims. Debtor shall advise Secured Party promptly
upon Debtor becoming aware that it owns any additional Commercial Tort Claims.
With respect to any new Commercial Tort Claim, Debtor will execute and deliver
such documents as Secured

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Party deems necessary to create, perfect and protect Secured Party's security
interest in such Commercial Tort Claim.

     6.13 Protection of Collateral. Debtor will do nothing to impair the rights
of Secured Party in the Collateral; provided that Debtor is permitted to use its
cash and cash equivalents so long as such use is not in violation of the Loan
Documents. Debtor assumes all liability and responsibility in connection with
the Collateral acquired by it, and the liability of Debtor to pay the Secured
Obligations shall in no way be affected or diminished by reason of the fact that
such Collateral may be lost, stolen, damaged, or for any reason whatsoever
unavailable to Debtor.

     6.14 Taxes and Claims. Debtor will pay when due all property and other
taxes, assessments and governmental charges imposed upon, and all claims
against, the Collateral (including claims for labor, materials and supplies);
provided that no such tax, assessment or charge need be paid if Debtor is
contesting the same in good faith by appropriate proceedings promptly instituted
and diligently conducted and if Debtor has established such reserve or other
appropriate provision, if any, as shall be required in conformity with GAAP; and
provided further that the same can be contested without risk of loss or
forfeiture or material impairment of the Collateral or the use thereof.

     6.15 Collateral Description. Debtor will furnish to Secured Party, from
time to time upon request, statements and schedules further identifying,
updating, and describing the Collateral and such other information, reports and
evidence concerning the Collateral as Secured Party may reasonably request, all
in reasonable detail.

     6.16 Use of Collateral. Debtor will not use or permit any Primary
Collateral to be used unlawfully or in violation of any provision of applicable
law, or any policy of insurance covering any of the Primary Collateral.

     6.17 Records of Collateral. Debtor shall keep full and accurate books and
records relating to the Collateral and shall stamp or otherwise mark such books
and records in such manner as Secured Party may reasonably request indicating
that the Collateral is subject to the Security Interests.

SECTION 7. Bank Accounts; Collection of Accounts and Payments

     Upon request by Secured Party, Debtor shall enter into a bank agency and
control agreement ("CONTROL AGREEMENT"), in a form specified by Secured Party,
with each financial institution with which Debtor maintains from time to time
any Deposit Accounts or Securities Accounts. Each Deposit Account or Securities
Account (which shall in no event include the Excluded Account) for which Debtor
has entered into a Control Agreement with the applicable financial institution
is referred to as a "PLEDGED ACCOUNT." Debtor hereby grants to Secured Party,
for the benefit of Secured Party and the Funds, a continuing lien upon, and
security interest in, all such accounts and all funds and other financial assets
at any time paid, deposited, credited or held in such accounts (whether for
collection, provisionally or otherwise) or otherwise in the possession of such
financial institutions, Securities Intermediaries and each such

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financial institution or Securities Intermediary shall act as Secured Party's
agent in connection therewith. Debtor shall not establish any Deposit Account or
Securities Account with any financial institution unless prior thereto Secured
Party and Debtor shall have entered into a Control Agreement with such financial
institution, unless otherwise consented to in writing by Secured Party. If
Secured Party delivers a Notice of Sole Control (as defined in the Control
Agreement) to any financial institution pursuant to the terms of any Control
Agreement, Secured Party shall promptly provide notice thereof to Debtor. If the
amount of the Secured Obligations is less than $5,000,000, then Secured Party
agrees that, upon the request of Debtor, it will reasonably cooperate with
Debtor to deliver any notices required under Section 2(f) of the Control
Agreement with Deutsche Bank Alex. Brown to reduce the Minimum Balance (as
defined in such Control Agreement) to an amount that is not less than the amount
of the Secured Obligations.

SECTION 8. Secured Party Appointed Attorney-in-Fact

     Debtor hereby irrevocably appoints Secured Party as Debtor's
attorney-in-fact, with full authority in the place and stead of Debtor and in
the name of Debtor, Secured Party or otherwise, from time to time in Secured
Party's discretion (but in the case of clauses (b), (d), (e), (f) and (g) below,
solely during the continuance of any Triggering Event or Event of Default) to
take any action and to execute any instrument that Secured Party may deem
necessary or advisable to accomplish the purposes of this Agreement, including,
without limitation:

          (a) to obtain and adjust insurance required to be paid to Secured
     Party;

          (b) to ask, demand, collect, sue for, recover, compound, receive and
     give acquittance and receipts for moneys due and to become due under or in
     respect of any of the Collateral;

          (c) to receive, endorse, and collect any drafts or other Instruments,
     Documents and Chattel Paper, in connection with clauses (a) and (b) above;

          (d) to file any claims or take any action or institute any proceedings
     that Secured Party may deem necessary or desirable for the collection of,
     or to preserve the value of, any of the Collateral or otherwise to enforce
     the rights of Secured Party with respect to any of the Collateral;

          (e) to pay or discharge taxes, liens or security interests levied or
     placed upon or threatened against the Collateral, the legality or validity
     thereof and the amounts necessary to discharge the same to be determined by
     Secured Party in its sole discretion, and such payments made by Secured
     Party to become obligations of Debtor to Secured Party, due and payable
     immediately without demand;

          (f) to sign and endorse any invoices, freight or express bills, bills
     of lading, storage or warehouse receipts, assignments, verifications and
     notices in connection with Accounts, Chattel Paper and other documents
     relating to the Collateral; and

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          (g) generally to take any act required of Debtor by Section 6 and to
     sell, transfer, pledge, make any agreement with respect to or otherwise
     deal with any of the Collateral as fully and completely as though Secured
     Party were the absolute owner thereof for all purposes, and to do, at
     Secured Party's option and Debtor's expense, at any time or from time to
     time, all acts and things that Secured Party deems necessary to protect,
     preserve or realize upon the Collateral.

Debtor hereby approves all acts of Secured Party made or taken pursuant to this
Section 8. Neither Secured Party nor any Person designated by Secured Party
shall be liable for any acts or omissions or for any error of judgment or
mistake of fact or law. This power, being coupled with an interest, is
irrevocable so long as this Agreement shall remain in force.

SECTION 9. Transfers and Other Liens

     Except as otherwise permitted herein or by the Notes, Debtor shall not:

          (a) sell, assign (by operation of law or otherwise) or otherwise
     dispose of, or grant any option with respect to, any of the Collateral,
     except in the ordinary course of its business and except that Debtor may
     use its cash and cash equivalents so long as such use is not in violation
     of the Loan Documents; or

          (b) create or suffer to exist any lien, security interest or other
     charge or encumbrance upon or with respect to any of the Collateral to
     secure indebtedness of any Person except for the security interest created
     by this Agreement.

SECTION 10. Remedies

     (a) If any Triggering Event or Event of Default shall have occurred and be
continuing, Secured Party may exercise in respect of the Collateral, in addition
to all other rights and remedies provided for herein or otherwise available to
it, all the rights and remedies of a secured party on default under the UCC
(whether or not the UCC applies to the affected Collateral) and also may: (i)
require Debtor to, and Debtor hereby agrees that it will, at its expense and
upon request of Secured Party forthwith, assemble all or part of the Collateral
as directed by Secured Party and make it available to Secured Party at any place
or places designated by Secured Party which is reasonably convenient to Secured
Party and Debtor in which event Debtor shall at its own expense (A) forthwith
cause the same to be moved to the place or places so designated by Secured Party
and thereby delivered to Secured Party, (B) store and keep any Collateral so
delivered to Secured Party at such place or places pending further action by
Secured Party, and (C) while Collateral shall be so stored and kept, provide
such guards and maintenance services as shall be necessary to protect the same
and to preserve and maintain the Collateral in good condition; (ii) withdraw all
cash in the Pledged Accounts and apply such monies in payment of the Secured
Obligations; and (iii) without notice except as specified below, sell, lease,
license or otherwise dispose of the Collateral or any part thereof by one or
more contracts, in one or more parcels at public or private sale, and without
the necessity

                                       12
<PAGE>

of gathering at the place of sale of the property to be sold, at any of the
Secured Party's offices or elsewhere, at such time or times, for cash, on credit
or for future delivery, and at such price or prices and upon such other terms as
Secured Party may deem commercially reasonable.

     (b) Debtor agrees that, to the extent notice of sale shall be required by
law, a reasonable authenticated notification of disposition shall be a
notification given at least ten (10) days prior to any such sale and such notice
shall (i) describe Secured Party and Debtor, (ii) describe the Collateral that
is the subject of the intended disposition, (iii) state the method of intended
disposition, (iv) state that the Debtor is entitled to an accounting of the
Secured Obligations and stating the charge, if any, for an accounting, and (v)
state the time and place of any public disposition or the time after which any
private sale is to be made. At any sale of the Collateral, if permitted by law,
Secured Party may bid (which bid may be, in whole or in part, in the form of
cancellation of indebtedness) for the purchase, lease, license or other
disposition of the Collateral or any portion thereof for the account of Secured
Party. Secured Party shall not be obligated to make any sale of Collateral
regardless of notice of sale having been given. Secured Party may disclaim any
warranties that might arise in connection with the sale, lease, license or other
disposition of the Collateral and have no obligation to provide any warranties
at such time. Secured Party may adjourn any public or private sale from time to
time by announcement at the time and place fixed therefor, and such sale may,
without further notice, be made at the time and place to which it was so
adjourned. To the extent permitted by law, Debtor hereby specifically waives all
rights of redemption, stay or appraisal which it has or may have under any law
now existing or hereafter enacted.

     (c) Upon the occurrence and during the continuance of a Triggering Event or
an Event of Default, Secured Party or its agents or attorneys shall have the
right without notice or demand or legal process (unless the same shall be
required by applicable law), personally, or by agents or attorneys, (i) to enter
upon, occupy and use any premises owned or leased by Debtor or where the
Collateral is located (or is believed to be located) until the Secured
Obligations are paid in full without any obligation to pay rent to Debtor, to
render the Collateral useable or saleable and to remove the Collateral or any
part thereof therefrom to the premises of Secured Party or any agent of Secured
Party for such time as Secured Party may desire in order to effectively collect
or liquidate the Collateral and use in connection with such removal any and all
services, supplies and other facilities of Debtor; and (ii) to take possession
of Debtor's original books and records, to obtain access to Debtor's data
processing equipment, computer hardware and Software relating to the Collateral
and to use all of the foregoing and the information contained therein in any
manner Secured Party deems appropriate.

     (d) Debtor acknowledges and agrees that a breach of any of the covenants
contained in Sections 6, 7 and 9 hereof will cause irreparable injury to Secured
Party and that Secured Party has no adequate remedy at law in respect of such
breaches and therefore agrees, without limiting the right of Secured Party to
seek and obtain specific performance of other obligations of Debtor contained in
this Agreement, that the covenants of Debtor contained in the Sections referred
to in this Section shall be specifically enforceable against Debtor.

                                       13
<PAGE>

SECTION 11. Assignment of Intellectual Property

     Debtor hereby assigns, transfers and conveys, effective upon the occurrence
of any Triggering Event or Event of Default, to Secured Party all Intellectual
Property owned or used by Debtor to the extent necessary to enable Secured Party
to realize on the Collateral and any successor or assign to enjoy the benefits
of the Collateral. This right and assignment shall inure to the benefit of
Secured Party and its successors, assigns and transferees, whether by voluntary
conveyance, operation of law, assignment, transfer, foreclosure, deed in lieu of
foreclosure or otherwise. Such right and assignment is granted free of charge,
without requirement that any monetary payment whatsoever including, without
limitation, any royalty or license fee, be made to Debtor or any other Person by
Secured Party.

SECTION 12. Assigned Agreements

     If a Triggering Event or an Event of Default has occurred and is
continuing, Debtor hereby irrevocably authorizes and empowers Secured Party,
without limiting any other authorizations or empowerments contained in any of
the other Loan Documents, to assert, either directly or on behalf of Debtor, any
claims Debtor may have, from time to time, against any other party to any of the
agreements to which Debtor is a party or to otherwise exercise any right or
remedy of Debtor under any such agreements (including, without limitation, the
right to enforce directly against any party to any such agreement all of
Debtor's rights thereunder, to make all demands and give all notices and to make
all requests required or permitted to be made by Debtor thereunder).

SECTION 13. Limitation on Duty of Secured Party with Respect to Collateral

     Beyond the safe custody thereof, Secured Party shall have no duties
concerning the custody and preservation of any Collateral in its possession (or
in the possession of any agent or bailee) or with respect to any income thereon
or the preservation of rights against prior parties or any other rights
pertaining thereto. Secured Party shall be deemed to have exercised reasonable
care in the custody and preservation of the Collateral in its possession if the
Collateral is accorded treatment substantially equal to that which it accords
its own property. Subject to the standards of the previous sentence, Secured
Party shall not be liable or responsible for any loss or damage to any of the
Collateral, or for any diminution in the value thereof, by reason of the act or
omission of any warehouseman, carrier, forwarding agency, consignee or other
agent or bailee selected by Secured Party in good faith.

SECTION 14. Application of Proceeds

     Upon the occurrence and during the continuance of an Event of Default or
Triggering Event, the proceeds of any collection, enforcement, sale or other
disposition of, or other realization upon, all or any part of the Collateral and
any cash held in the Pledged Accounts shall be applied as follows. first, to all
expenses and fees due and owing to Secured Party or any Fund; second, to all
accrued and unpaid interest on the Notes; and third, to principal of the Notes
and any other remaining secured obligations.

                                       14
<PAGE>

SECTION 15. Expenses

     Debtor shall pay all costs, fees and expenses of Secured Party or any Fund
(a) protecting, storing, warehousing, appraising, insuring, handling,
maintaining and shipping the Collateral, (b) creating, perfecting and enforcing
the Security Interests (other than the initial expenses incurred by Secured
Party or any Fund in connection with creating and perfecting the Security
Interests in the Collateral existing as of the date hereof), (c) maintaining the
Security Interests to the extent circumstances affecting the Security Interests
change after the date hereof and (d) collecting, enforcing, retaking, holding,
preparing for disposition, processing and disposing of the Collateral. Debtor
shall also pay any and all excise, property, sales and use taxes imposed by any
federal, state, local or foreign authority on any of the Collateral, or with
respect to periodic appraisals and inspections of the Collateral, or with
respect to the sale or other disposition thereof. If Debtor fails to promptly
pay any portion of the above costs, fees and expenses when due or to perform any
other obligation of Debtor under this Agreement, Secured Party may, at its
option, but shall not be required to, pay or perform the same and charge
Debtor's account for all fees, costs and expenses incurred therefor, and Debtor
agrees to reimburse Secured Party or such Fund therefor on demand. All sums so
paid or incurred by Secured Party or any Fund for any of the foregoing, any and
all other sums for which Debtor may become liable hereunder and all fees, costs
and expenses (including attorneys' fees, legal expenses and court costs)
incurred by Secured Party or any Fund in enforcing or protecting the Security
Interests or any of their rights or remedies under this Agreement shall be
payable on demand, shall constitute Secured Obligations, shall bear interest
until paid at the highest rate provided in the Notes and shall be secured by the
Collateral.

SECTION 16. Termination of Security Interests; Release of Collateral

     Upon payment in full of all Secured Obligations, the Security Interests
shall terminate and all rights to the Collateral shall revert to Debtor. Upon
such termination of the Security Interests or release of any Collateral, Secured
Party will, at the expense of Debtor, execute and deliver to Debtor such
documents (including the delivery of any termination notices for any Pledged
Account) as Debtor shall reasonably request to evidence the termination of the
Security Interests or the release of such Collateral, as the case may be.

SECTION 17. Notices

     All notices, approvals, requests, demands and other communications
hereunder shall be given in accordance with Section 9(f) of the Securities
Purchase Agreement.

SECTION 18. Successors and Assigns

     This Agreement is for the benefit of Secured Party and the Funds and their
respective successors and assigns, and in the event of an assignment of all or
any of the Secured Obligations, the rights hereunder, to the extent applicable
to the Secured Obligations so assigned, may be transferred with such Secured
Obligations. This Agreement shall be binding on Debtor

                                       15
<PAGE>

and its successors and assigns; provided that Debtor may not delegate its
obligations under this Agreement without Secured Party's prior written consent.

SECTION 19. Changes in Writing

     No amendment, modification, termination or waiver of any provision of this
Agreement shall be effective unless the same shall be in writing signed by
Secured Party.

SECTION 20. Applicable Law

     THIS AGREEMENT SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN
ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO
CONFLICT OF LAWS PRINCIPLES.

SECTION 21. Failure or Indulgence Not Waiver; Remedies Cumulative

     No failure or delay on the part of Secured Party or any Fund in the
exercise of any power, right or privilege hereunder shall impair such power,
right or privilege or be construed to be a waiver of any default or acquiescence
therein, nor shall any single or partial exercise of any such power, right or
privilege preclude other or further exercise thereof or any other right, power
or privilege. All rights and remedies existing under this Agreement are
cumulative to, and not exclusive of, any rights or remedies otherwise available.

SECTION 22. Headings

     Section and subsection headings in this Agreement are included herein for
convenience of reference only and shall not constitute a part of this Agreement
for any other purpose or be given any substantive effect.

SECTION 23. Counterparts

     This Agreement may be executed in any number of counterparts, all of which
taken together shall constitute one and the same instrument and any of the
parties hereto may execute this Agreement by signing any such counterpart;
provided that a facsimile signature shall be considered due execution and shall
be binding upon the signatory thereto with the same force and effect as if the
signature were an original and not a facsimile thereof.

SECTION 24. Survival

     All representations and warranties of Debtor contained in this Agreement
shall survive the execution and delivery of this Agreement.

                    Balance of Page Intentionally Left Blank
                             Signature Page Follows

                                       16
<PAGE>

     Witness the due execution of this Security Agreement by the respective duly
authorized officers of the undersigned as of the date first written above.

                                       Debtor:

                                       ZIX CORPORATION, a Texas corporation

                                       By: /s/ Ronald A. Woessner
                                           -------------------------------------
                                       Title: S.V.P.
                                              ----------------------------------

                                       Secured Party:

                                       PROMETHEAN ASSET MANAGEMENT
                                       L.L.C., a Delaware limited liability
                                       company, in its capacity as collateral
                                       agent for the Funds

                                       By: /s/ James F. O'Brien
                                           -------------------------------------
                                       Title: James F. O'Brien, Managing Member
                                              ----------------------------------<PAGE>

                                                                    EXHIBIT 4.9

                                     FORM OF
                             SUBORDINATION AGREEMENT

         THIS SUBORDINATION AGREEMENT (this "AGREEMENT"), dated as of _______
__, 200__ is among ZIX CORPORATION, a Texas corporation ("BORROWER" and together
with its Subsidiaries (as defined in Section 1 below) sometimes hereinafter are
referred to individually as a "LOAN PARTY" and collectively as "LOAN PARTIES"),
________________, a ___________ [entity] ("SUBORDINATED LENDER"), and PROMETHEAN
ASSET MANAGEMENT L.L.C., a Delaware limited liability company, in its capacity
as agent ("AGENT") for the Lenders (as defined in Section 1 below).

                                    RECITALS

         A. Borrower and Lenders have entered into a certain Securities Purchase
Agreement dated as of September __, 2002 (as the same has been and hereafter may
be amended, modified, supplemented or restated, the "SECURITIES PURCHASE
AGREEMENT"), pursuant to which Borrower issued and sold the Convertible Notes
(as defined in Section 1 below) to the Lenders.

         B. Borrower granted, and may hereafter grant, to Agent, for the benefit
of Agent and the Lenders, a first priority security interest in its assets and
property pursuant to a certain security agreement (as the same may be amended,
modified, supplemented or restated from time to time, the "SECURITY AGREEMENT")
among Borrower and Agent, to secure its indebtedness, liabilities and
obligations under the Loan Documents (as defined in Section 1 below).

         C. Subordinated Lender and Borrower have entered, or are about to
enter, into that certain [_____________________] (as the same may be amended,
modified, supplemented or restated in accordance with the terms hereof, the
"SUBORDINATED LOAN AGREEMENT"), pursuant to which [BORROWER IS OBLIGATED TO PAY
TO SUBORDINATED LENDER A CERTAIN AMOUNT OF MONEY] (the "SUBORDINATED LOANS").
The Subordinated Loans shall be evidenced by certain promissory notes issued in
accordance with the terms of the Subordinated Loan Agreement and made by
Borrower payable to the order of Subordinated Lender (such promissory notes,
together with any and all promissory notes issued in replacement or substitution
therefor, in each case as the same may be amended, modified, supplemented or
restated from time to time, hereinafter are referred to as the "SUBORDINATED
NOTES").

         D. As an inducement to and as one of the conditions precedent to the
obligation of Agent and Lenders to permit the incurrence of the Subordinated
Indebtedness (as defined in Section 1 below), Agent and Lenders have required
the execution and delivery by Subordinated Lender and Borrower of this
Agreement.

<PAGE>

         NOW, THEREFORE, in order to induce Agent and Lenders to permit the
incurrence of the Subordinated Indebtedness, and for other good and valuable
consideration, the receipt and sufficiency of which hereby are acknowledged, the
parties hereto hereby agree as follows:

         1. DEFINITIONS. The following terms shall have the following meanings
in this Agreement:

                  AGENT shall have the meaning ascribed to such term in the
         preamble of this Agreement, or shall mean any other person hereafter
         appointed by the holders of the Senior Indebtedness as agent for
         themselves for the purposes of this Agreement.

                  CONVERTIBLE NOTES means the secured convertible notes of the
         Borrower issued pursuant to the Securities Purchase Agreement, as they
         may be amended from time to time, and any secured convertible notes
         issued in exchange therefor or replacement thereof, including upon any
         transfer of any principal amount of the Convertible Notes.

                  ENFORCEMENT ACTION is defined in Section 2.7.

                  JUNIOR COLLATERAL means all of the property and interests in
         property, tangible, real or personal, if any, now owned or hereafter
         acquired by any Loan Party, in or upon which any Loan Party has granted
         or may hereafter grant a Junior Lien, and including, without
         limitation, all proceeds and products of such property and interests in
         property.

                  JUNIOR LIENS means all liens, collateral assignments,
         mortgages and security interests, if any, previously or hereafter
         granted by any Loan Party or any other Person to Subordinated Lender
         securing in whole or in part any of the Subordinated Indebtedness.

                  LENDER OR LENDERS shall mean any "Buyer" or the "Buyers,"
         respectively, as such terms are defined in the Securities Purchase
         Agreement; provided that upon transfer of any principal amount of the
         Convertible Notes, such terms shall refer to any holder or all of the
         holders, respectively, of the Senior Indebtedness.

                  LOAN DOCUMENTS means the Securities Purchase Agreement, the
         Convertible Notes, the Security Agreement and each of the other
         agreements entered into by the Borrower and/or the Lenders in
         connection therewith.

                  LOAN PARTIES is defined in the preamble of this Agreement.

                  PROCEEDING is defined in Section 2.3.

                  SENIOR COLLATERAL means all of the property and interests in
         property, tangible, real or personal, now owned or hereafter acquired
         by any Loan Party, in or upon which any Loan Party has granted a Senior
         Lien, and including, without limitation, all proceeds and products of
         such property and interests in property.

                                       2
<PAGE>

                  SENIOR INDEBTEDNESS shall mean any and all indebtedness,
         obligations and liabilities of every nature incurred by Borrower under
         the Loan Documents, including any accrued interest or other payments
         from time to time owing the Agent and/or any Lenders under the Loan
         Documents, including, without limitation, the principal amount of all
         debts, claims and indebtedness, accrued and unpaid interest and all
         fees, costs and expenses, whether primary, secondary, direct,
         contingent, fixed or otherwise, heretofore, now and from time to time
         hereafter owing, due or payable, whether before or after the filing of
         a Proceeding under the Bankruptcy Law (as defined in the Convertible
         Notes) together with (a) any amendments, modifications, renewals or
         extensions thereof to the extent not prohibited by the terms of this
         Agreement and (b) any interest accruing thereon after the commencement
         of a Proceeding, without regard to whether or not such interest is an
         allowed claim.

                  SENIOR LIENS means all liens, collateral assignments,
         mortgages and security interests previously or hereafter granted by any
         Loan Party or any other Person to Agent or the Lenders, for the benefit
         of Agent and/or the Lenders, and their respective successors, assigns
         and participants, securing in whole or in part any of the Senior
         Indebtedness.

                  SUBORDINATED DEFAULT shall mean a default in the payment of
         the Subordinated Indebtedness or in the performance of any term,
         covenant or condition contained in the Subordinated Loan Instruments,
         or any other occurrence permitting Subordinated Lender to accelerate or
         demand payment of all or any portion of the Subordinated Indebtedness.

                  SUBORDINATED DEFAULT NOTICE shall mean a written notice to
         Agent pursuant to which Agent is notified of the existence of a
         Subordinated Default.

                  SUBORDINATED INDEBTEDNESS shall mean all of the Subordinated
         Loans and any and all other indebtedness, liabilities and obligations
         of Borrower and its Subsidiaries to Subordinated Lender evidenced by
         the Subordinated Notes and all other amounts now or hereafter owed by
         the Loan Parties, or any of them, to Subordinated Lender pursuant to
         the Subordinated Loan Instruments.

                  SUBORDINATED LOAN INSTRUMENTS shall mean the Subordinated
         Notes, the Subordinated Loan Agreement, any guaranty with respect to
         the Subordinated Indebtedness and all other agreements, documents and
         instruments evidencing or pertaining to any portion of the Subordinated
         Indebtedness.

                  SUBSIDIARIES mean any entity in which the Borrower, directly
         or indirectly, owns capital stock or holds an equity or similar
         interest, other than entities in which the Borrower (i) has less than
         25% of the voting control of such entity, (ii) has less than 25% of the
         equity interest in such entity and (iii) has no exposure to any
         liability, contingent or

                                       3
<PAGE>

         otherwise, that could result in a Material Adverse Effect (as defined
         in the Securities Purchase Agreement).

         2. SUBORDINATION OF SUBORDINATED INDEBTEDNESS TO SENIOR INDEBTEDNESS.

                  2.1 SUBORDINATION. The payment of any and all of the
         Subordinated Indebtedness hereby expressly is subordinated, to the
         extent and in the manner set forth herein, to the indefeasible payment
         in full, in cash and/or through conversion of the Convertible Notes in
         accordance with the terms of the Convertible Notes, of the Senior
         Indebtedness. Each holder of Senior Indebtedness, whether now
         outstanding or hereafter arising, shall be deemed to have acquired
         Senior Indebtedness in reliance upon the provisions contained herein.

                  2.2 RESTRICTION ON PAYMENTS. Notwithstanding any provision of
         the Subordinated Loan Instruments to the contrary and in addition to
         any other limitations set forth herein or therein, no payment of
         principal, interest or any other amount due with respect to the
         Subordinated Indebtedness shall be made by Borrower or received by
         Subordinated Lender, and Subordinated Lender shall not exercise any
         right of set-off or recoupment with respect to the Subordinated
         Indebtedness, at any time when any Convertible Notes are outstanding,
         when any other amounts are due to Agent or any Lender with respect to
         the Senior Indebtedness or when Agent or any Lender has an outstanding
         payment claim against Borrower with respect to the Senior Indebtedness;
         provided, however, that amounts not in excess of $50,000, individually
         or in the aggregate, that are the subject of a bona fide dispute
         between Borrower and Agent or any Lender shall not be considered an
         "outstanding payment claim" for purposes of this sentence.

                  2.3 PROCEEDINGS. In the event of any insolvency, bankruptcy,
         receivership, custodianship, liquidation, reorganization, assignment
         for the benefit of creditors or other proceeding for the liquidation,
         dissolution or other winding up of Borrower or any of its Subsidiaries
         or any of their respective properties (a "PROCEEDING"), (i) all Senior
         Indebtedness first shall be paid in full in cash before any payment of
         or with respect to the Subordinated Indebtedness shall be made; (ii)
         any payment which, but for the terms hereof, otherwise would be payable
         or deliverable in respect of the Subordinated Indebtedness, shall be
         paid or delivered directly to Agent (to be held and/or applied by Agent
         in accordance with the terms of the Collateral Agency Agreement of even
         date herewith by and among Agent and Lenders (the "AGENCY AGREEMENT")
         until all Senior Indebtedness is paid in full in cash, and Subordinated
         Lender irrevocably authorizes, empowers and directs all receivers,
         trustees, debtors-in-possession, liquidators, custodians, conservators
         and others having authority in the premises to effect all such payments
         and deliveries, and Subordinated Lender also irrevocably authorizes,
         empowers and directs Agent to demand, sue for, collect and receive
         every such payment or distribution; (iii) Subordinated Lender agrees to
         execute and deliver to Agent or its representative all such further
         instruments confirming the authorization referred to in the

                                       4
<PAGE>

         foregoing clause (ii); and (iv) Subordinated Lender may execute,
         verify, deliver and file any proofs of claim in respect of the
         Subordinated Indebtedness and hereby irrevocably authorizes, empowers
         and appoints Agent its agent and attorney-in-fact to (A) execute,
         verify, deliver and file such proofs of claim upon the failure of
         Subordinated Lender promptly to do so within fifteen (15) days prior to
         the expiration of the time to file any such proof and (B) vote such
         proofs of claim in any such Proceeding; provided Agent shall have no
         obligation to execute, verify, deliver, file and/or vote any such proof
         of claim. In the event that Agent votes any claim in accordance with
         the authority granted hereby, Subordinated Lender shall not be entitled
         to change or withdraw such vote. The Senior Indebtedness shall continue
         to be treated as Senior Indebtedness and the provisions of this
         Agreement shall continue to govern the relative rights and priorities
         of Agent, Lenders and Subordinated Lender even if all or part of the
         Senior Indebtedness or the security interests securing the Senior
         Indebtedness are subordinated, set aside, avoided or disallowed in
         connection with any such proceeding and this Agreement shall be
         reinstated if at any time any payment of any of the Senior Indebtedness
         is rescinded or must otherwise be returned by any holder of the Senior
         Indebtedness or any representative of such holder.

                  2.4 INCORRECT PAYMENTS. If any payment is received by
         Subordinated Lender on account of the Subordinated Indebtedness at a
         time when such payment is prohibited by Section 2.2, such payment shall
         not be commingled with any asset of Subordinated Lender, shall be held
         in trust by Subordinated Lender for the benefit of Agent and the
         Lenders and shall promptly be paid over to Agent, or its designated
         representative, for application (in accordance with the Agency
         Agreement) to the payment of the Senior Indebtedness then remaining
         unpaid, until all of the Senior Indebtedness is paid in full.

                  2.5 SALE, TRANSFER. Subordinated Lender shall not sell,
         assign, dispose of or otherwise transfer all or any portion of the
         Subordinated Indebtedness without the prior written consent of Agent
         and the Lenders, which consent may be given or withheld in their sole
         and absolute discretion. In the event of a permitted sale, assignment,
         disposition or other transfer, Subordinated Lender, prior to the
         consummation of any such action, shall cause the transferee thereof to
         execute and deliver to Agent an agreement substantially identical to
         this Agreement, providing for the continued subordination and
         forbearance of the Subordinated Indebtedness to the Senior Indebtedness
         as provided herein and for the continued effectiveness of all of the
         rights of Lenders and Agent arising under this Agreement.
         Notwithstanding the failure to execute or deliver any such agreement,
         the subordination effected hereby shall survive any sale, assignment,
         disposition or other transfer of all or any portion of the Subordinated
         Indebtedness, and the terms of this Agreement shall be binding upon the
         successors and assigns of Subordinated Lender, as provided in Section
         11 below.

                  2.6 LEGENDS. Until the Senior Indebtedness is paid in full,
         each of the Subordinated Loan Instruments at all times shall contain in
         a conspicuous manner the following legend:

                                       5
<PAGE>

                  "This Note [or other Subordinated Loan Instrument] and the
                  indebtedness evidenced hereby are subordinate in the manner
                  and to the extent set forth in that certain Subordination
                  Agreement (the "SUBORDINATION AGREEMENT") dated as of
                  _____________________ ____, 200__ among Zix Corporation
                  ("BORROWER"), _____________ and Promethean Asset Management
                  L.L.C., a Delaware limited liability company ("AGENT"), to the
                  indebtedness (including interest) owed by Borrower to the
                  holders of all of the notes issued pursuant to that certain
                  Securities Purchase Agreement dated as of September __, 2002
                  among Borrower and the purchasers thereunder, as such
                  Securities Purchase Agreement has been and hereafter may be
                  supplemented and amended from time to time; and each holder of
                  this Note [or other Subordinated Loan Instrument], by its
                  acceptance hereof, shall be bound by the provisions of the
                  Subordination Agreement."

                  2.7 RESTRICTION ON ACTION BY SUBORDINATED LENDER.

                  (a) Until the Senior Indebtedness is paid in full and
         notwithstanding anything contained in the Subordinated Loan Instruments
         or the Loan Documents to the contrary, Subordinated Lender shall not,
         without the prior written consent of Agent, which consent may be
         granted or withheld in Agent's sole and absolute discretion, agree to
         any amendment, modification or supplement to the Subordinated Loan
         Instruments the effect of which is to (i) alter the subordination
         provisions with respect to the Subordinated Indebtedness, including,
         without limitation, subordinating the Subordinated Indebtedness to any
         other debt, (ii) shorten the maturity date of any of the Subordinated
         Indebtedness or otherwise alter the repayment terms of the Subordinated
         Indebtedness in a manner which would cause the Subordinated
         Indebtedness to mature or require repayment prior to the Maturity Date
         (as defined in the Convertible Notes) or (iii) take any lien or
         security interest in any Senior Collateral.

                  (b) Until the Senior Indebtedness is paid in full, in cash
         and/or through conversion of the Convertible Notes in accordance with
         the terms of the Convertible Notes, Subordinated Lender shall not,
         without the prior written consent of Agent, which consent may be
         granted or withheld in Agent's sole and absolute discretion, (i) take
         any action to collect or enforce payment of the Subordinated
         Indebtedness or (ii) exercise any of the remedies with respect to the
         Subordinated Indebtedness and/or the Junior Collateral, as set forth in
         any of the Subordinated Loan Instruments or that otherwise may be
         available to Subordinated Lender, either at law or in equity by
         judicial proceedings or otherwise (an "ENFORCEMENT ACTION"). Any
         distributions or other proceeds of any Enforcement Action obtained by
         Subordinated Lender in violation of the foregoing prohibition shall in
         any event be held in trust by it for the benefit of Agent and Lenders
         and promptly paid or delivered to Agent for the benefit of Lenders in
         the form received until all Senior Debt is indefeasibly paid in full in
         cash and/or through conversion of the Convertible Notes in accordance
         with the terms of the Convertible Notes.

                                       6
<PAGE>

                  2.8 BANKRUPTCY FINANCING ISSUES. This Agreement shall continue
         in full force and effect after the filing of any petition ("PETITION")
         by or against any Loan Party under the Bankruptcy Law (as defined in
         the Convertible Notes) and all converted or succeeding cases in respect
         thereof. All references herein to a Loan Party shall be deemed to apply
         to such Loan Party as debtor-in-possession and to a trustee for such
         Loan Party. If any Loan Party shall become subject to a Proceeding
         under the Bankruptcy Law (as defined in the Convertible Notes), and if
         Agent or any Lender shall desire to permit such Loan Party to use cash
         collateral or to provide post-Petition financing (or liens to secure
         same) from Agent or such Lender to such Loan Party under the Bankruptcy
         Law (as defined in the Convertible Notes), Subordinated Lender agrees
         as follows: (1) adequate notice to Subordinated Lender shall be deemed
         to have been provided for such permission or post-Petition financing if
         Subordinated Lender receives notice thereof three (3) Business Days (or
         such shorter notice as has been approved by the bankruptcy court for
         creditors in general) prior to the hearing in respect of such use of
         cash collateral or such financing and (2) no objection will be raised
         by Subordinated Lender to any such use by such Loan Party of cash
         collateral on the grounds of a failure to provide adequate protection
         for any Junior Lien on the Junior Collateral.

                                       7
<PAGE>

         3. COLLATERAL MATTERS.

                  3.1 VALIDITY OF SENIOR LIENS. Subordinated Lender agrees that
         it will not contest the validity, perfection, priority or
         enforceability of the Senior Liens and that as between Subordinated
         Lender on the one hand and Agent and Lenders on the other hand, the
         terms of this Agreement shall govern even if all or part of the Senior
         Indebtedness or the Senior Liens are avoided, disallowed, set aside or
         otherwise invalidated in any judicial proceeding or otherwise.

                  3.2 MANAGEMENT OF COLLATERAL. Until such time as all amounts
         due or to become due on or in respect of Senior Indebtedness have been
         paid in full, Agent and Lenders shall have the exclusive and unfettered
         right to manage, perform and enforce the terms of the Loan Documents
         with respect to all Senior Collateral and to exercise and enforce all
         privileges and rights thereunder according to their discretion and
         exercise of their business judgment, including, without limitation, the
         exclusive right to take or retake control or possession of the Senior
         Collateral and to hold, prepare for sale, process, sell, lease,
         foreclose upon, collect, exercise rights or remedies with respect to,
         dispose of, or liquidate the Senior Collateral, and Subordinated Lender
         shall not take or seek to take any such action. In connection
         therewith, Subordinated Lender waives any and all rights to affect the
         method or challenge the appropriateness of any action by Agent and/or
         the Lenders and hereby consents to Agent and/or the Lenders dealing
         with the Senior Collateral as if the Subordinated Lender shall not have
         had any security interest therein, irrespective of whether any Senior
         Collateral constitutes proceeds of any Junior Collateral.

                  3.3 NOTICES AND WAIVER OF MARSHALING. Subordinated Lender,
         Agent and each Lender each acknowledges that this Agreement shall
         constitute notice of their respective interests, if any, in the Senior
         Collateral as provided by Section 9-504 of the Uniform Commercial Code
         in the applicable jurisdiction and each hereby waives any right to
         compel any marshaling of any of the Senior Collateral. To the extent
         that Agent or any Lender has possession of any Senior Collateral while
         any Subordinated Indebtedness is outstanding, Agent or such Lender in
         possession acknowledges notice of the security interest in such Senior
         Collateral of the Subordinated Lender for the purposes of Section 9-305
         of the Texas Uniform Commercial Code and acknowledges that it is
         holding any such Senior Collateral constituting certificated securities
         for Subordinated Lender for the purposes of Section 8-301 of the Texas
         Uniform Commercial Code.

                  3.4 INSURANCE PROCEEDS. Proceeds of the Junior Collateral, if
         any, and Senior Collateral include insurance proceeds, and therefore,
         notwithstanding the terms set forth in the Subordinated Loan Instrument
         to the contrary, the priorities set forth in Section 2 hereof govern
         the ultimate disposition of casualty insurance proceeds. Identifiable
         proceeds of Junior Collateral, if any, shall be maintained in a manner
         that segregates them from any Senior Collateral. If and to the extent
         any identifiable proceeds from Junior Collateral are commingled or
         otherwise deposited into any account representing

                                       8
<PAGE>

         Senior Collateral, such proceeds shall be deemed to be, and Junior
         Creditor hereby agrees they are, Senior Collateral.

         4. CONTINUED EFFECTIVENESS OF THIS AGREEMENT. The terms of this
Agreement, the subordination effected hereby, and the rights and the obligations
of Subordinated Lender, Agent and Lenders arising hereunder, shall not be
affected, modified or impaired in any manner or to any extent by: (a) any
amendment or modification of or supplement to any Loan Document or any
Subordinated Loan Instrument; (b) the validity or enforceability of any of such
documents; or (c) any exercise or non-exercise of any right, power or remedy
under or in respect of the Senior Indebtedness or the Subordinated Indebtedness
or any of the instruments or documents referred to in clause (a) above.

         5. REPRESENTATIONS AND WARRANTIES. Subordinated Lender hereby
represents and warrants to Agent as follows:

                  5.1 EXISTENCE AND POWER. Subordinated Lender is a [SPECIFY
         ENTITY TYPE] duly organized, validly existing and in good standing
         under the laws of the State of [_________].

                  5.2 AUTHORITY. Subordinated Lender has full power and
         authority to enter into, execute, deliver and carry out the terms of
         this Agreement and to incur the obligations provided for herein, all of
         which have been duly authorized by all proper and necessary action and
         are not prohibited by the organizational documents of Subordinated
         Lender.

                  5.3 BINDING AGREEMENTS. This Agreement, when executed and
         delivered, will constitute the valid and legally binding obligation of
         Subordinated Lender enforceable in accordance with its terms, except as
         such enforceability may be limited by applicable bankruptcy,
         insolvency, reorganization, moratorium or similar laws affecting the
         enforcement of creditors' rights generally and by equitable principles.

                  5.4 CONFLICTING AGREEMENTS; LITIGATION. No provisions of any
         mortgage, indenture, contract, agreement, statute, rule, regulation,
         judgment, decree or order binding on Subordinated Lender or affecting
         the property of Subordinated Lender conflicts with, or requires any
         consent which has not already been obtained under, or would in any way
         prevent the execution, delivery or performance of the terms of this
         Agreement. The execution, delivery and carrying out of the terms of
         this Agreement will not constitute a default under, or result in the
         creation or imposition of, or obligation to create, any lien upon the
         property of Subordinated Lender pursuant to the terms of any such
         mortgage, indenture, contract or agreement. No pending or, to the best
         of Subordinated Lender's knowledge, threatened, litigation, arbitration
         or other proceedings if adversely determined would in any way prevent
         the performance of the terms of this Agreement.

                                       9
<PAGE>

                  5.5 NO DIVESTITURE. Subordinated Lender is the current owner
         and holder of the Subordinated Note and all other Subordinated Loan
         Instruments.

                  5.6 SENIOR COLLATERAL. Subordinated Lender has no, and will
         not take any, Junior Liens on any of the Senior Collateral.

         6. CUMULATIVE RIGHTS, NO WAIVERS. Each and every right, remedy and
power granted to Agent or Lenders hereunder shall be cumulative and in addition
to any other right, remedy or power specifically granted herein, in the Loan
Documents or now or hereafter existing in equity, at law, by virtue of statute
or otherwise, and may be exercised by Agent or Lenders, from time to time,
concurrently or independently and as often and in such order as Agent or Lenders
may deem expedient. Any failure or delay on the part of Agent or Lenders in
exercising any such right, remedy or power, or abandonment or discontinuance of
steps to enforce the same, shall not operate as a waiver thereof or affect
Agent's or Lenders' right thereafter to exercise the same, and any single or
partial exercise of any such right, remedy or power shall not preclude any other
or further exercise thereof or the exercise of any other right, remedy or power,
and no such failure, delay, abandonment or single or partial exercise of Agent's
or Lenders' rights hereunder shall be deemed to establish a custom or course of
dealing or performance among the parties hereto.

         7. MODIFICATION. Any modification of any provision of this Agreement
shall not be effective in any event unless the same is in writing and signed by
Agent and Subordinated Lender. Any waiver of any provision of this Agreement, or
any consent to any departure by a party therefrom, shall not be effective in any
event unless the same is in writing and signed by the party against whom
enforcement is sought, and then such modification, waiver or consent shall be
effective only in the specific instance and for the specific instance and for
the specific purpose given. Any notice to or demand on Subordinated Lender in
any event not specifically required of Agent hereunder shall not entitle
Subordinated Lender to any other or further notice or demand in the same,
similar or other circumstances unless specifically required hereunder.

         8. ADDITIONAL DOCUMENTS AND ACTIONS. Subordinated Lender at any time,
and from time to time, after the execution and delivery of this Agreement, upon
the request of Agent and at the expense of Borrower, promptly will execute and
deliver such further reasonable documents and do such further reasonable acts
and things as Agent may request in order to effect fully the purposes of this
Agreement.

                                       10
<PAGE>

         9. NOTICES. Any notices, consents, waivers or other communications
required or permitted to be given under the terms of this Agreement must be in
writing and will be deemed to have been delivered: (i) upon receipt, when
delivered personally; (ii) upon receipt, when sent by facsimile (provided
confirmation of transmission is mechanically or electronically generated and
kept on file by the sending party); or (iii) one (1) Business Day after deposit
with a nationally recognized overnight delivery service, in each case properly
addressed to the party to receive the same. The addresses and facsimile numbers
for such communications shall be:

                  To Subordinated
                                   ------------------------------------
                  Lender:
                                   ------------------------------------

                                   ------------------------------------

                                   Attention:
                                                     --------------------------
                                   Facsimile:
                                                     --------------------------

                  with a copy to:
                                   ------------------------------------

                                   ------------------------------------

                                   ------------------------------------

                                   Attention:
                                                     --------------------------
                                   Facsimile:
                                                     --------------------------

                  To Borrower:     Zix Corporation
                                   2711 North Haskell Avenue
                                   Suite 2300, LB 36
                                   Dallas, Texas 75204-2960
                                   Attention:        General Counsel
                                   Facsimile:        (214) 515-7385

                  with a copy to:  Hughes & Luce, LLP
                                   111 Congress Avenue, Suite 900
                                   Austin, Texas 78701
                                   Attention:        Bryan C. Wittman, Esq.
                                   Facsimile:        (512) 482-6859

                  To Agent:        Promethean Asset Management L.L.C.
                                   750 Lexington Avenue, 22nd Floor
                                   New York, New York 10022
                                   Attention:        David M. Kittay
                                                     Greg Carney
                                   Facsimile:        (212) 758-9334

                                       11

<PAGE>

                  With a copy to:  Katten Muchin Zavis Rosenman
                                   525 West Monroe Street
                                   Suite 1600
                                   Chicago, Illinois  60661
                                   Attention:        Robert J. Brantman, Esq.
                                   Facsimile:        (312) 902-1061

If to a Lender, to it at the address and facsimile number set forth on the
Schedule of Buyers to the Securities Purchase Agreement, with copies to such
Lender's representatives as set forth on the Schedule of Buyers to the
Securities Purchase Agreement, or, in the case of a Lender or any other party
named above, at such other address and/or facsimile number and/or to the
attention of such other person as the recipient party has specified by written
notice given to each other party five (5) days prior to the effectiveness of
such change. Written confirmation of receipt (A) given by the recipient of such
notice, consent, waiver or other communication, (B) mechanically or
electronically generated by the sender's facsimile machine containing the time,
date, recipient facsimile number and an image of the first page of such
transmission or (C) provided by a nationally recognized overnight delivery
service shall be rebuttable evidence of personal service, receipt by facsimile
or receipt from a nationally recognized overnight delivery service in accordance
with clause (i), (ii) or (iii) above, respectively.

         10. SEVERABILITY. If any provision of this Agreement shall be invalid
or unenforceable in any jurisdiction, such invalidity or unenforceability shall
not affect the validity or enforceability of the remainder of this Agreement in
that jurisdiction or the validity or enforceability of any provision of this
Agreement in any other jurisdiction.

         11. SUCCESSORS AND ASSIGNS. This Agreement shall inure to the benefit
of the successors and assigns of Agent and Lenders and shall be binding upon the
successors and assigns of Subordinated Lender and Borrower.

         12. COUNTERPARTS. This Agreement may be executed in two or more
identical counterparts, all of which shall be considered one and the same
agreement and shall become effective when counterparts have been signed by each
party and delivered to the other party; provided that a facsimile signature
shall be considered due execution and shall be binding upon the signatory
thereto with the same force and effect as if the signature were an original, not
a facsimile signature.

         13. DEFINES RIGHTS OF CREDITORS. The provisions of this Agreement are
solely for the purpose of defining the relative rights of Subordinated Lender,
Agent and Lenders and shall not be deemed to create any rights or priorities in
favor of any other Person, including, without limitation, Borrower. The failure
of Borrower to make any payment to Subordinated Lender due to the operation of
this Agreement shall not be construed as prohibiting the occurrence of a
Subordinated Default.

                                       12
<PAGE>

         14. CONFLICT. In the event of any conflict between any term, covenant
or condition of this Agreement and any term, covenant or condition of any of the
Subordinated Loan Instruments, the provisions of this Agreement shall control
and govern. For purposes of this Section 14, to the extent that any provisions
of any of the Subordinated Loan Instruments provide rights, remedies and
benefits to Agent or Lenders that exceed the rights, remedies and benefits
provided to Agent or Lenders under this Agreement, such provisions of the
applicable Subordinated Loan Instruments shall be deemed to supplement (and not
to conflict with) the provisions hereof.

         15. STATEMENT OF INDEBTEDNESS TO SUBORDINATED LENDER. Borrower will
furnish to Agent upon demand, a statement of the indebtedness owing from
Borrower to Subordinated Lender, and will give Agent access to the books of
Borrower so that Agent can make a full examination of the status of such
indebtedness.

         16. HEADINGS. The headings of this Agreement are for convenience of
reference and shall not form part of, or affect the interpretation of, this
Agreement.

         17. TERMINATION. This Agreement shall terminate upon the indefeasible
payment in full of the Senior Indebtedness.

         18. SUBORDINATED DEFAULT NOTICE. Subordinated Lender and Borrower each
shall provide Agent with a Subordinated Default Notice upon the occurrence of
each Subordinated Default, and Subordinated Lender shall notify Agent in the
event such Subordinated Default is cured or waived. Agent shall promptly furnish
to Subordinated Lender notice of the acceleration of any Senior Indebtedness,
provided, that subject to the terms and conditions of this Agreement, the
failure to furnish such notice to the Subordinated Lender shall not be
actionable by any person and shall not have any effect upon any of the rights
and obligations of the parties hereto or any of the rights of the Subordinated
Lender on account of any acceleration of Senior Indebtedness.

         19. NO CONTEST OF SUBORDINATED INDEBTEDNESS. Agent and the Lender each
agree that it will not, and will not encourage any other person to, at any time,
contest the validity or enforceability of the Subordinated Indebtedness, except
in connection with the exercise of rights under this Agreement and as a lender
with senior priority to Subordinated Lender.

         20. NO CONTEST OF SENIOR INDEBTEDNESS OR SENIOR LIENS. Subordinated
Lender agrees that it will not, and will not encourage any other person to, at
any time, contest the validity, perfection, priority or enforceability of the
Senior Indebtedness or the Senior Liens in the Senior Collateral granted to
Agent pursuant to the Loan Documents.

         21. GOVERNING LAW; JURISDICTION; JURY TRIAL. All questions concerning
the construction, validity, enforcement and interpretation of this Agreement
shall be governed by the internal laws of the State of New York, without giving
effect to any choice of law or conflict of law provision or rule (whether of the
State of New York or any other jurisdiction) that would

                                       13
<PAGE>

cause the application of the laws of any jurisdiction other than the State of
New York. Each party hereby irrevocably submits to the exclusive jurisdiction of
the state and federal courts sitting in the City of New York, borough of
Manhattan, for the adjudication of any dispute hereunder or in connection
herewith or with any transaction contemplated hereby or discussed herein, and
hereby irrevocably waives, and agrees not to assert in any suit, action or
proceeding, any claim that it is not personally subject to the jurisdiction of
any such court, that such suit, action or proceeding is brought in an
inconvenient forum or that the venue of such suit, action or proceeding is
improper. Each party hereby irrevocably waives personal service of process and
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address for such notices to it under
this Agreement and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.
EACH PARTY HEREBY IRREVOCABLY WAIVES ANY RIGHT IT MAY HAVE, AND AGREES NOT TO
REQUEST, A JURY TRIAL FOR THE ADJUDICATION OF ANY DISPUTE HEREUNDER OR IN
CONNECTION HEREWITH OR ARISING OUT OF THIS AGREEMENT OR ANY TRANSACTION
CONTEMPLATED HEREBY.

                [remainder of this page intentionally left blank]

                                       14
<PAGE>

         IN WITNESS WHEREOF, Subordinated Lender, Borrower and Agent have caused
this Subordination Agreement to be executed as of the date first above written.

                            SUBORDINATED LENDER:

                            [NAME]

                            By:
                               ---------------------------------------
                            Name:
                                 -------------------------------------
                            Title:
                                  ------------------------------------

                            BORROWER:

                            ZIX CORPORATION

                            By:
                               ---------------------------------------
                            Name:
                                 -------------------------------------
                            Title:
                                  ------------------------------------

                            AGENT:

                            PROMETHEAN ASSET MANAGEMENT L.L.C.,
                            in its capacity as agent for all Lenders

                            By:
                               ---------------------------------------
                            Name:
                                 -------------------------------------
                            Title:
                                  ------------------------------------

                                       15

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