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                                                                   EXHIBIT 10.18

                                 ZIX CORPORATION
                             STOCK OPTION AGREEMENT
                      (2003 NEW EMPLOYEE STOCK OPTION PLAN)

Date of Grant                                                    Expiration Date

December 16, 2003                                              December 15, 2013

         THIS STOCK OPTION AGREEMENT ("Agreement") is made and entered into as
of the 18th day of December, 2003 by and between Zix Corporation, a Texas
corporation (the "Company"), and Bradley Almond ("Optionee").

         WHEREAS, the Company wishes to recognize the contributions of the
Optionee to the Company and to encourage the Optionee's sense of proprietorship
in the Company by owning the Common Stock, par value $.01 per share (the "Common
Stock"), of the Company;

         NOW, THEREFORE, in consideration of the mutual agreements and covenants
contained herein, the Company hereby grants to the Optionee a non-qualified
stock option ("Option") to purchase up to a total of 100,000 shares of the
Common Stock at a price per share of $6.40 (the "Option Price") on the terms and
conditions and subject to the restrictions as set forth in this Agreement and
the provisions in the Zix Corporation 2003 New Employee Stock Option Plan (which
is incorporated herein by reference) (the "Plan"). All defined terms contained
herein shall have the meanings ascribed to them in the Plan, except as otherwise
provided herein.

1.       DEFINITIONS.

         a.       Acquiring Person. An "Acquiring Person" shall mean any person
(including any "person" as such term is used in Sections 13(d)(3) or 14(d)(2) of
the Securities Exchange Act of 1934, as amended (the "Exchange Act") that,
together with all Affiliates and Associates of such person, is the beneficial
owner of 35% or more of the outstanding Common Stock. The term "Acquiring
Person" shall not include the Company, any subsidiary of the Company, any
employee benefit plan of the Company or subsidiary of the Company, or any person
to the extent such person is holding Common Stock for or pursuant to the terms
of any such plan. For the purposes of this Agreement, a person who becomes an
Acquiring Person by acquiring beneficial ownership of 35% or more of the Common
Stock at any time after the date of this Agreement shall continue to be an
Acquiring Person whether or not such person continues to be the beneficial owner
of 35% or more of the outstanding Common Stock.

         b.       Affiliate and Associate. "Affiliate" and "Associate" shall
have the respective meanings ascribed to such terms in Rule 12b-2 of the General
Rules and Regulations under the Exchange Act in effect on the date of this
Agreement.

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         c.       Change in Control. A "Change in Control" of the Company shall
have occurred if at any time during the term of this Agreement any of the
following events shall occur:

                  (i) Any Sale of the Company; or

                  (ii) Any Acquiring Person has become the beneficial owner of
         securities which, when added to any securities already owned by such
         person, would represent in the aggregate 35% or more of the
         then-outstanding securities of the Company that are entitled to vote to
         elect any class of directors;

                  (iii) If at any time, the Continuing Directors then serving on
         the Board of Directors of the Company cease for any reason to
         constitute at least a majority thereof; or

                  (iv) Any occurrence that would be required to be reported in
         response to Item 6(e) of Schedule 14A of Regulation 14A or any
         successor rule or regulation promulgated under the Exchange Act.

         d.       Continuing Director. A "Continuing Director" shall mean a
director of the Company who (i) is not an Acquiring Person or an Affiliate or
Associate thereof, or a representative of an Acquiring Person or nominated for
election by an Acquiring Person, and (ii) was either a member of the Board of
Directors of the Company on the date of this Agreement or subsequently became a
director of the Company and whose initial election or initial nomination for
election by the Company's shareholders was approved by a majority of the
Continuing Directors then on the Board of Directors of the Company.

         e.       Disability. "Disability" shall mean any medically determinable
physical or mental impairment that, in the opinion of the Committee, based upon
medical reports and other evidence satisfactory to the Committee, can reasonably
be expected to prevent the Optionee from performing substantially all of his or
her customary duties of employment (with or without reasonable accommodation)
for a continuous period of not less than 12 months.

         f.       Person. A "Person" shall mean an individual, a corporation, a
partnership, an association, a joint-stock company, a trust, an incorporated
organization, or a government or political subdivision thereof and any other
entity. A Person, together with that Person's Affiliates and Associates, and any
Persons acting as a partnership, limited partnership, joint venture,
association, syndicate, or other group (whether or not formally organized), or
otherwise acting jointly or in concert or in a coordinated or consciously
parallel manner (whether or not pursuant to any express agreement), for the
purpose of acquiring, holding, voting, or disposing of securities of the Company
with that Person, shall be deemed a single "Person."

         g.       Resignation. "Resignation" shall mean the voluntary
termination by the Optionee of his or her employment relationship with the
employing Subsidiary and, if applicable, Company under circumstances other than
Retirement.

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         h.       Retirement. "Retirement" shall mean the termination of
Optionee's employment in accordance with the requirements of a written
retirement plan, policy or rule of the Company that has been duly adopted by the
Company or employing Subsidiary, as applicable.

         i.       Sale. A "Sale" occurs with respect to the Company if it
engages in a merger, consolidation, or sale, lease, license, transfer, or other
effective disposition of all or substantially all of the Company's assets and
the Company or its shareholders or Affiliates immediately before such
transaction beneficially own, immediately after or as a result of such
transaction, equity securities of the surviving or acquiring corporation or such
corporation's parent corporation possessing less than fifty-one percent (51%) of
the voting power of the surviving or acquiring Person or such Person's parent
corporation, provided that a Sale shall not be deemed to occur upon any public
offering or series of such offerings of securities of the Company that results
in any such change in beneficial ownership.

2.       TERM OF OPTION. The term of this Option shall expire on the date set
forth in the upper right hand corner on page 1 of this Agreement (the "stated
term"), except as such term may be otherwise shortened by the other provisions
of the Plan or this Agreement.

3.       EXERCISE OF OPTION.

         a.       Exercise. This Option shall become exercisable in increments
as follows:

<TABLE>
<CAPTION>
                           Date Upon Which Right
Number of Shares            To Purchase Accrues
----------------           ---------------------
<S>                        <C>
    25,000                 Immediately vested
    25,000                 December 16, 2004
     6,250                 March 16, 2005
     6,250                 June 16, 2005
     6,250                 September 16, 2005
     6,250                 December 16, 2005
     6,250                 March 16, 2006
     6,250                 June 16, 2006
     6,250                 September 16, 2006
     6,250                 December 16, 2006
</TABLE>

         Except as provided in the Plan or this Agreement, the Option shall not
be exercisable unless Optionee shall, at the time of exercise, be an employee of
the Company or a Subsidiary, and once the Option has become exercisable with
respect to a certain number of shares as provided above, it shall thereafter be
exercisable as to all of that number of shares, or as to any part thereof, until
expiration or termination of this Option. However, this Option may not be
exercised as to less than 100 shares at any one time (or the remaining shares
then purchasable under this Option, if less than 100 shares).

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         b.       Adjustment. In the event there is any adjustment to the Common
Stock subject to Section 5(b) of the Plan, the Board of Directors or Committee
shall make such adjustment as it deems appropriate to the number of shares
subject to Award or to the Option Price, or both.

         c.       Exercise - Change in Control. If the Optionee is still an
employee of the Company or a Subsidiary on the date of the occurrence of a
Change in Control, this Option shall become exercisable in full on such date and
may be exercised at any time or times thereafter and until expiration or
termination of this Option; provided, however, that this Option may not be
exercised as to less than 100 shares at any one time (or the remaining shares
then purchasable under this Option, if less than 100 shares).

         d.       Method of Exercise. This Option may be exercised only by
written notice (the "Exercise Notice") by the Optionee to the Company at its
principal executive office. The Exercise Notice shall be deemed given when
deposited in the U.S. mails, postage prepaid, addressed to the Company at its
principal executive office, or if given other than by deposit in the U.S. mails,
when delivered in person to an officer of the Company at that office. The date
of exercise of this Option (the "Exercise Date") shall be the date of the
postmark if the notice is mailed or the date received if the notice is delivered
other than by mail. The Exercise Notice shall state the number of shares in
respect of which this Option is being exercised and, if the shares for which
this Option is being exercised are to be evidenced by more than one stock
certificate, the denominations in which the stock certificates are to be issued.
The Exercise Notice shall be signed by the Optionee and shall include the
complete address of such person, together with such person's social security
number.

         This Option may be exercised either by tendering cash in the amount of
the Option Price or, with the Company's consent, by tendering shares of Common
Stock (which may include shares previously acquired upon exercise of options
granted under the Plan). The Exercise Notice shall be accompanied by payment of
the aggregate Option Price of the shares purchased by cash, a certified
cashier's check or, at the Company's option, by delivery of shares of Common
Stock having a Fair Market Value on the date immediately preceding the exercise
date equal to the Option Price.

         If the shares to be purchased are covered by an effective registration
statement under the Securities Act of 1933, as amended, any option granted under
the Plan may be exercised by a broker-dealer acting on behalf of an Optionee if
(a) the broker-dealer has received from the Optionee or the Company a fully- and
duly-endorsed agreement evidencing such option, together with instructions
signed by the Optionee requesting the Company to deliver the shares of Common
Stock subject to such option to the broker-dealer on behalf of the Optionee and
specifying the account into which such shares should be deposited, (b) adequate
provision has been made with respect to the payment of any withholding taxes due
upon such exercise, and (c) the broker-dealer and the Optionee have otherwise
complied with Section 220.3(e)(4) of Regulation T, 12 CFR Part 220, or any
successor provision.

         The certificates for shares of Common Stock as to which this Option
shall have been so exercised shall be registered in the name of the Optionee and
shall be delivered to the Optionee at

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the address specified in the Exercise Notice. An option exercise shall be valid
only if the Optionee makes payment or other arrangements relating to the
withholding tax obligations discussed in Paragraph 8. In the event the person
exercising this Option is a transferee of the Optionee by will or under the laws
of descent and distribution, the Exercise Notice shall be accompanied by
appropriate proof of the right of such transferee to exercise this Option.

4.       TERMINATION OF OPTION.

         In the event an Optionee ceases to be an employee of either the Company
or a Subsidiary of the Company due to death, Retirement, Resignation, Disability
or termination by the Company for any reason other than "cause" (such five
events each being a "Qualified Termination"), this Option may be exercised by
the Optionee or his or her estate, personal representative or beneficiary to the
fullest extent that the Optionee was entitled to exercise the same on the day
immediately prior to such termination (i) at any time within the one-year period
commencing on the day next following such termination if such termination is due
to the death of the Optionee; (ii) at any time within the 30-day period
commencing on the day next following the effective date of such termination if
such termination is due to the Resignation of the Optionee; or (iii) at any time
within the six-month period commencing on the day next following such
termination in the case of any other Qualified Termination (or in any such case
in (i), (ii) or (iii) above, if shorter, only for the remaining stated term of
this Option). In the event that the Optionee's employment is terminated for any
reason other than a Qualified Termination, this Option shall automatically
expire simultaneously with such termination. For purposes of this Paragraph,
"cause" shall mean (i) the failure, in the sole opinion of the Company or a
Subsidiary of the Company that employs Optionee, of Optionee to adequately
perform the duties assigned to Optionee (other than any such failure resulting
from Optionee's Disability); (ii) the engagement by Optionee in misconduct that,
in the sole opinion of the Company or a Subsidiary of the Company that employs
Optionee, is or may have the effect of being materially injurious to the Company
or its Subsidiaries; or (iii) the conviction of Optionee of any felony or crime
of moral turpitude.

         After the Optionee's death, this Option shall be exercisable only by
the executor or administrator of the Optionee's estate, or if the Optionee's
estate is not in administration, by the person or persons to whom the Optionee's
rights shall have passed by the Optionee's will or under the laws of descent and
distribution of the state where the Optionee was domiciled at the date of death.

5.       NO RIGHTS AS SHAREHOLDER. Neither the Optionee nor any person claiming
under or through the Optionee shall be or have any rights or privileges of a
shareholder of the Company in respect of any of the shares issuable upon the
exercise of this Option, unless and until certificates representing such shares
shall have been issued (as evidenced by the appropriate entry on the books of
the Company or of a duly authorized transfer agent of the Company).

6.       STATE AND FEDERAL SECURITIES REGULATION. No shares shall be issued by
the Company upon the exercise of this Option unless and until any
then-applicable requirements of state and federal laws and regulatory agencies
shall have been fully complied with to the satisfaction of the Company and its
counsel. The Company may suspend for a reasonable period or periods the

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                                                               Change in Control

time during which this Option may be exercised if, in the opinion of the
Company, such suspension is required to enable the Company to remain in
compliance with regulatory requirements relating to the issuance of shares of
Common Stock subject to this Option. This Option is subject to the requirement
that, if at any time the Company shall determine, in its discretion, that the
listing, registration or qualification of the shares of common stock subject to
this Option upon any securities exchange or under any state or federal law, or
the consent or approval of any government regulatory body, is necessary or
desirable as a condition of, or in connection with, the granting or exercise of
this Option or the issue or purchase of shares under this Option, this Option
may not be exercised in whole or in part until such listing, registration,
qualification, consent or approval shall have been effected or obtained free of
any conditions not acceptable to the Company. The Company shall be under no
obligation to effect or obtain any such listing, registration, qualification,
consent or approval if the Company shall determine, in its discretion, that such
action would not be in the best interest of the Company. The Company shall not
be liable for damages due to a delay in the delivery or issuance of any stock
certificates for any reason whatsoever, including, but not limited to, a delay
caused by listing, registration or qualification of the shares of Common Stock
subject to an option upon any securities exchange or under any federal or state
law or the effecting or obtaining of any consent or approval of any governmental
body with respect to the granting or exercise of this Option or the issue or
purchase of shares under this Option.

7.       MODIFICATION OF OPTIONS. At any time and from time-to-time the
Committee may execute an instrument providing for modification, extension, or
renewal of any outstanding option, provided that no such modification, extension
or renewal shall impair this Option in any respect without the written consent
of the holder of this Option.

8.       WITHHOLDING OF TAXES. The Company may make such provisions and take
such steps as it may deem necessary or appropriate for the withholding of any
taxes which the Company or any Subsidiary is required by any law or regulation
of any governmental authority, whether federal, state or local, domestic or
foreign, to withhold in connection with any option, including, but not limited
to, the withholding of the issuance of all or any portion of the shares of
Common Stock subject to this Option until the Optionee reimburses the Company or
the applicable Subsidiary for the amount the Company or the applicable
Subsidiary is required to withhold with respect to such taxes, canceling any
portion of the issuance in an amount sufficient to reimburse the Company or the
applicable Subsidiary for the amount it is required to so withhold, or taking
any other action reasonably required to satisfy the withholding obligation of
the Company or the applicable Subsidiary.

9.       CONTINUED EMPLOYMENT NOT PRESUMED. Nothing in this Agreement, the Plan
or any document describing it nor the grant of an option shall give the Optionee
the right to continue in employment with the Company or any of its Subsidiaries
or affect the right of the Company or a Subsidiary to terminate the employment
of the Optionee with or without cause.

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                                                               Change in Control

10.      NON-COMPETITION COVENANTS.

         a.       The provisions of this subparagraph a. shall apply both during
normal working hours and at all other times including, but not limited to,
nights, weekends and vacation time, while Optionee is employed by the Company or
any Subsidiary. Optionee shall not directly or indirectly (i) engage in any
employment, business, or activity that is competitive with the business of the
Company or any Subsidiary, (ii) assist any other person or organization in
competing with, or in preparing to engage in competition with, the business of
the Company or any Subsidiary. Direct competition shall include, but not be
limited to, the design, development, production, promotion or sale of products,
software, or services competitive with those of the Company or any Subsidiary.
In addition, Optionee shall not directly or indirectly (i) engage in any
employment, business, or activity that is competitive with either (A) the
proposed business of the Subsidiary that employs Optionee ("Employing
Subsidiary") or (B) any proposed business of any of the Company's other
Subsidiaries (the "Non-Employing Subsidiaries") of which Optionee has actual
knowledge, or (ii) assist any other person or organization in competing with, or
in preparing to engage in competition with, either (A) the proposed business of
the Employing Subsidiary or (B) any proposed business of any Non-Employing
Subsidiary of which Optionee has actual knowledge.

         b.       The provisions of this subparagraph b. shall apply during
Optionee's employment with the Company or any Subsidiary and for a period of six
months after Optionee ceases to be employed by the Company or any Subsidiary.
Optionee shall not directly or indirectly solicit to conduct any Competitive
Business with, or conduct any Competitive Business with, any (i) then-current
customer of the Employing Subsidiary or (ii) any person that has been a customer
of the Employing Subsidiary within the six months prior to the time of
Optionee's separation from employment. The phrase "Competitive Business" means
the line(s) of business(es) conducted by the Employing Subsidiary.

         c.       The provisions of this subparagraph c. shall apply during
Optionee's employment with the Company or any Subsidiary and for a period of 12
months after Optionee's separation from employment. Optionee shall not directly
or indirectly solicit to hire, or cause to be hired, any employee of the Company
or any Subsidiary as an employee or agent of, or consultant to, any business
enterprise that Optionee is associated with.

         d.       Each non-competition covenant of Optionee contained in the
preceding provisions of this Paragraph 10 (the "non-competition covenant") shall
be construed as an agreement independent of any other provision of this
Agreement and the existence of any claim or cause of action of Optionee against
the Company or any Subsidiary, whether predicated on this Agreement or
otherwise, shall not constitute a defense to the enforcement by the Company or
any Subsidiary of such non-competition covenant.

         e.       The Company and Optionee have in good faith used their best
efforts to make each non-competition covenant contained in the preceding
provisions of this Paragraph 10 reasonable in both scope and in duration. It is
not anticipated, nor is it intended, by either party

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                                                               Change in Control

to this Agreement that any court or other tribunal having jurisdiction over the
matter will find it necessary to reform any non-competition covenant to make it
reasonable in both scope and in duration, or otherwise. If any non-competition
covenant is deemed by a tribunal having jurisdiction over the matter to be
unlawful or unenforceable, such provision will be deemed severable from this
Agreement and such provision will be limited or eliminated to the minimum extent
necessary so that the remaining provisions of this Agreement shall otherwise
remain in full force and effect and be enforceable. Furthermore, in lieu of such
unlawful or unenforceable provision, there shall be added automatically as part
of this Agreement a provision as similar in terms as may be possible and be
enforceable.

         f.       Optionee is agreeing to the provisions of this Paragraph 10 in
consideration of the grant of this Option. The provisions of this Paragraph 10
shall be valid and enforceable by the Company and its Subsidiaries, regardless
of whether or not any of this Option granted hereunder actually becomes
exercisable, or whether or not Optionee actually exercises any rights under this
Option. In the event of any conflict or inconsistency between any provision of
this Paragraph 10 and any similar or analogous provision of any other agreement
(either currently in effect or that may be entered into in the future) between
Optionee, on the one hand, and the Company or any Subsidiary, on the other hand,
whichever provision is most favorable to the Company or such Subsidiary shall
govern.

11.      OPTION ISSUED PURSUANT TO PLAN. This Option is issued pursuant to and
subject to the terms and conditions and the restrictions as set forth in the
Plan, and in the event of any inconsistency, the provisions of the Plan shall
govern, provided that no amendment shall be made to the Plan subsequent to the
date hereof that impairs the Optionee's rights under this Option without the
Optionee's written consent.

12.      NO LIABILITY OF OPTION. This Option is not liable for or subject to, in
whole or in part, the debts, contracts, liabilities or torts of the Optionee nor
shall it be subject to garnishment, attachment, execution, levy or other legal
or equitable process.

13.      NO ASSIGNMENT. This Option is not transferable otherwise than by will
or the laws of descent and distribution, and is exercisable during the
Optionee's lifetime only by Optionee. Without limiting the generality of the
foregoing, this Option may not be assigned, transferred (except as aforesaid),
pledged or hypothecated in any way (whether by operation of law or otherwise),
and shall not be subject to execution, attachment, or similar process, without
the prior written consent of the Company. Any attempted assignment, transfer,
pledge, or hypothecation contrary to the provisions hereof shall be void and
ineffective for all purposes.

14.      GOVERNING LAW. This Agreement has been executed in, and shall be deemed
to be performable in, Dallas, Dallas County, Texas. The parties agree that this
Agreement shall be governed by and construed in accordance with the laws of the
State of Texas (excluding its conflict of laws rules). The parties further agree
that the courts of the State of Texas, and any courts whose jurisdiction is
derivative on the jurisdiction of the courts of the State of Texas, shall have
personal jurisdiction over all parties to this Agreement.

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15.      ENTIRE AGREEMENT. Except for the Plan, this Agreement constitutes the
entire agreement between the parties pertaining to the subject matter hereof and
supersedes all prior and contemporaneous agreements, representations and
understandings of the parties. No supplement, modification or amendment of this
Agreement shall be binding unless executed in writing by the party to be charged
therewith. No waiver of any of the provisions of this Agreement shall be deemed,
or shall constitute a waiver of any other provision, whether or not similar, nor
shall any waiver constitute a continuing waiver.

16.      DUPLICATE ORIGINALS. Duplicate originals of this document shall be
executed by both the Company and the Optionee, each of which shall retain one
duplicate original.

17.      NOTICE. Other than any Exercise Notice, any notice required or
permitted to be given under the Plan or this Agreement shall be in writing and
delivered in person or sent by registered or certified mail, return receipt
requested, first-class postage prepaid, (i) if to the Optionee, at the address
shown on the books and records of the Company or at the Optionee's place of
employment, or (ii) if to the Company, at 2711 N. Haskell Avenue, Suite 2300, LB
36, Dallas, Texas 75204-2960: Attention: Treasurer, or any other address that
may be given by either party to the other party by notice pursuant to this
Paragraph. Any notice other than any Exercise Notice, if sent by registered or
certified mail, shall be deemed to have been given when received.

                                    ZIX CORPORATION

                                    By: /s/ John A. Ryan
                                        --------------------------------------
                                        John A. Ryan
                                        President and Chief Executive Officer

OPTIONEE:

/s/  Bradley Almond
---------------------------
Bradley Almond

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