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                                                                     EXHIBIT 4.5

                              AMENDED AND RESTATED
                          REGISTRATION RIGHTS AGREEMENT

            THIS AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT, dated as
of__________, 2005 (this "Agreement"),______________ by and between ZIX
CORPORATION, a Texas corporation (the "Company"), and ______________,
a____________ (the "Investor").

                              W I T N E S S E T H:

            WHEREAS, in connection with the Purchase Agreement (such capitalized
term and all other capitalized terms used herein having the respective meanings
provided herein), the Company has agreed to provide certain registration rights
under the 1933 Act and applicable state securities laws with respect to the
Registrable Securities issuable upon conversion, exercise or redemption of, or
otherwise in connection with, the securities issued pursuant to the Purchase
Agreement;

            WHEREAS, the Company and the Investor have previously executed and
delivered, one to the other, the Original Registration Rights Agreement; and

            WHEREAS, in connection with the execution and delivery by the
Company and the Investor, one to the other, of the Purchase Agreement Amendment,
the Company and the Investor wish to amend and restate the Original Registration
Rights Agreement upon the terms and subject to the conditions provided in this
Agreement.

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

            1.    DEFINITIONS.

            (a)   As used in this Agreement, the terms "Agreement," "Company"
and "Investor" shall have the respective meanings assigned to such terms in the
introductory paragraph of this Agreement.

            (b)   All the agreements or instruments herein defined shall mean
such agreements or instruments as the same may from time to time be supplemented
or amended or the terms thereof waived or modified to the extent permitted by,
and in accordance with, the terms thereof and of this Agreement.

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            (c)   The following terms shall have the following meanings (such
meanings to be equally applicable to both the singular and plural forms of the
terms defined):

            "Additional Registrable Securities" means any shares of Common Stock
which are included within the definition of Registrable Securities but not
required by this Agreement to be included in any Registration Statement filed
pursuant to Section 2(a)(i) below.

            "Allowed Delay" shall have the meaning provided in Section 2(c)(ii).

            "AMEX" means the American Stock Exchange, Inc.

            "Approved Market" shall have the meaning provided in Section
2(c)(i).

            "Availability Date" shall have the meanings provided in Section
3(m).

            "Closing Warrant" means the Amended and Restated Common Stock
Purchase Warrant issued by the Company to the Investor pursuant to the Purchase
Agreement, as such warrant has been amended and restated pursuant to the
Purchase Agreement Amendment, and any similar instrument issued upon transfer or
split up thereof.

            "Common Stock" means the Common Stock, par value $0.01 per share, of
the Company.

            "Compensation Event" shall have the meaning provided in Section
2(c)(i).

            "Compensation Payments" shall have the meaning provided in Section
2(c)(i).

            "Compensation Period" shall have the meaning provided in Section
2(c)(i).

            "Compensation Rate" shall mean the rate of one percent per month
during the first 30 days in the aggregate in which any one or more Compensation
Periods are in effect and two percent per month thereafter.

            "Conversion Price" shall have the meaning provided in the Note.

            "Holder" means the Investor and each subsequent holder of the Note,
the Warrants, Registrable Securities or Additional Registrable Securities, or
any

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portion thereof which subsequent holder has rights under this Agreement assigned
to it in accordance with Section 7(c).

            "Initial Registrable Securities Amount" shall have the meaning
provided in Section 2(a)(i).

            "Interest Share Price" shall have the meaning provided in the Note.

            "1934 Act" means the Securities Exchange Act of 1934, as amended,
and the rules and regulations promulgated thereunder.

            "1933 Act" means the Securities Act of 1933, as amended, and the
rules and regulations promulgated thereunder.

            "NASD" means the National Association of Securities Dealers, Inc.

            "Nasdaq" means the Nasdaq National Market.

            "Note" means the Amended and Restated Convertible Note due 2005-2008
issued by the Company pursuant to the Purchase Agreement and amended and
restated as provided in the Purchase Agreement Amendment.

            "NYSE" means the New York Stock Exchange, Inc.

            "Original Registration Rights Agreement" means the Registration
Rights Agreement, dated as of November 2, 2004, by and between the Company and
Investor.

            "Other Registration Rights Agreements" means the several Amended and
Restated Registration Rights Agreements, dated as of the date hereof, by and
between the Company and the several investors parties thereto who purchased or
acquired Amended and Restated Convertible Notes due 2005-2008 and Common Stock
Purchase Warrants issued by the Company.

            "Principal Market" means the Nasdaq or such other U.S. market or
exchange which is the principal market on which the Common Stock is then listed
for trading.

            "Prospectus" means the prospectus forming part of or relating to any
Registration Statement, as amended or supplemented by any prospectus supplement,
with respect to the terms of the offering of any portion of the Registrable
Securities or Additional Registrable Securities covered by such Registration
Statement and by all other amendments and supplements to the

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prospectus, including post-effective amendments and all material incorporated by
reference in such prospectus.

            "Purchase Agreement" means the Purchase Agreement, dated as of
November 1, 2004, by and between the Company and the Investor, as amended by the
Purchase Agreement Amendment.

            "Purchase Agreement Amendment" means Amendment No. 1 to Purchase
Agreement, dated as of April , 2005, by and -- between the Company and the
Investor.

            "Purchase Price" when used with respect to a particular Warrant,
shall have the meaning provided in such Warrant.

            "Redemption Warrant" shall have the meaning provided in the Note.

            "register," "registered" and "registration" refer to a registration
made by preparing and filing a registration statement or similar document in
compliance with the 1933 Act, and the declaration or ordering of effectiveness
of such registration statement or document by the SEC.

            "Registrable Securities" means (i) the Underlying Shares, the
Warrant Shares and the shares of Common Stock or other securities issued or
issuable to each Holder or its permitted transferee or designee (a) upon
conversion or redemption of the Note and upon exercise of the Warrants, or (b)
upon any distribution with respect to, any exchange for or any replacement of
the Note or the Warrants, or (c) upon any conversion, exercise or exchange of
any securities issued in connection with any such distribution, exchange or
replacement; (ii) securities issued or issuable upon any stock split, stock
dividend, recapitalization or similar event with respect to the Common Stock or
other securities referred to in clause (i) of this definition; and (iii) any
other security issued as a dividend or other distribution with respect to, in
exchange for, or in replacement of, the Note, the Warrants or the securities
referred to in the preceding clauses of this definition.

            "Registration Insufficiency Event" shall have the meaning provided
in Section 2(a)(i).

            "Registration Period" shall have the meaning provided in Section
3(a).

            "Registration Statement" shall mean any registration statement of
the Company filed under the 1933 Act that covers the resale of any of the
Registrable Securities or Additional Registrable Securities pursuant to the
provisions of this Agreement, amendments and supplements to such Registration
Statement,

                                      -4-

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including post-effective amendments, all exhibits and all material incorporated
by reference in such Registration Statement.

            "SEC" means the U.S. Securities and Exchange Commission.

            "Share Redemption" shall have the meaning provided in the Note.

            "Share Redemption Date" shall have the meaning provided in the Note.

            "Trading Day" means at any time a day on which the securities
exchange or market that at such time constitutes the Principal Market is open
for general trading of securities.

            "Underlying Shares" means the shares of Common Stock issuable or
issued upon conversion of, or otherwise in respect of or in exchange for, the
Note or any other security (other than the Redemption Warrant) issued in respect
of or in exchange for the Note, including, without limitation, shares of Common
Stock issuable pursuant to Section 2(c) of the Note.

            "VWAP" means for any Trading Day the volume-weighted average price
of the Common Stock on the Principal Market, as reported by Bloomberg Financial
L.P. (based on a Trading Day from 9:30 a.m., Eastern Time, to 4:00 p.m., Eastern
Time) using the AQR function, on such Trading Day.

            "Warrants" means, collectively, the Closing Warrant and the
Redemption Warrant.

            "Warrant Shares" means the shares of Common Stock issuable upon
exercise of, or otherwise in respect of, the Warrants.

            (d)   Capitalized terms used herein but not otherwise defined herein
shall have the respective meanings assigned to such terms in the Purchase
Agreement.

            2.    REGISTRATION.

            (a)   REGISTRATION STATEMENTS.

            (i)   REGISTRABLE SECURITIES. Promptly following the Closing Date
(but, subject to Section 2(a)(iii), no later than 30 days after the Closing
Date), the Company shall prepare and file with the SEC one Registration
Statement on Form S-3 covering the resale of the Registrable Securities in an
amount at least equal to the sum of (1) 150% of the number of Underlying Shares
that would be issuable

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upon conversion of the Note in full or, in case the Note were to be redeemed
pursuant to Section 2(b) thereof, upon exercise of the Redemption Warrant in
full for cash plus (2) 150% of the number of shares of Common Stock issuable
upon exercise of the Closing Warrant in full for cash, plus (3) such number of
additional Registrable Securities as the Company wishes to have available to
issue in lieu of cash payment of interest on the Note, in each case in the
preceding clauses (1) through (3), determined without regard to any restrictions
on beneficial ownership contained in the Note, the Warrants or the Purchase
Agreement (such sum the "Initial Registrable Securities Amount"). Such
Registration Statement also shall cover, to the extent permitted by the 1933 Act
and the rules promulgated thereunder (including Rule 416), such indeterminate
number of additional shares of Common Stock resulting from stock splits, stock
dividends or similar transactions with respect to the Registrable Securities. No
securities other than the Registrable Securities and the securities being
registered by the Company in accordance with the Other Registration Rights
Agreements shall be included in the Registration Statement without the consent
of the Holder. If at any time the number of Registrable Securities of the types
specified in clauses (1) and (2) of the definition of Initial Registrable
Securities Amount that is included in a Registration Statement and remaining
unsold thereunder shall be insufficient to cover the resale of Registrable
Securities in an amount at least equal to 140% of the sum of:

            (x)   the number of Underlying Shares issued and remaining unsold
      under the Registration Statement, or that would be issuable, upon
      conversion in full of the Note or, in case the Note were to be redeemed
      pursuant to Section 2(b) thereof, upon exercise of the Redemption Warrant
      in full for cash plus

            (y)   without duplication of the amount specified in the preceding
      clause (x), the number of shares of Common Stock that have been issued and
      remain unsold under the Registration Statement, or would be issuable, upon
      redemption of the Note pursuant to Section 2(c) of the Note as required by
      Section 2(d)(2) of the Note, determined on any date (A) as if such date
      were a Share Redemption Date on which all remaining outstanding principal
      installments required by Section 2(d)(2) of the Note to be redeemed
      pursuant to Section 2(c) of the Note were being redeemed on such date of
      determination, and (B) without regard to any limitation on the number of
      shares of Common Stock issuable in such Share Redemption by reason of any
      Share Redemption Daily Limitation or Section 2(c)(9) of the Note plus

            (z)   the number of shares of Common Stock issued and remaining
      unsold under the Registration Statement, or that would be issuable upon
      exercise of the Warrants outstanding at such time in full for cash,

                                      -6-

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in each case in the preceding clauses (x) through (z) determined without regard
to any restrictions on beneficial ownership contained in the Note, the Warrants
or the Purchase Agreement (a "Registration Insufficiency Event"), then promptly,
but in no event later than 30 days after such insufficiency shall occur, the
Company shall file with the SEC an additional Registration Statement on Form S -
3 (or, if Form S-3 is not then available to the Company, on such form of
registration statement as is then available to effect a registration for resale
of such additional Registrable Securities) covering such number of shares of
Common Stock as shall be sufficient to cover such amount. Except as set forth
above, the requirements with respect to a subsequent Registration Statement
shall be the same as those applicable to the initial Registration Statement.

            (ii)  ADDITIONAL REGISTRABLE SECURITIES. At any time and from time
to time, promptly following the written demand of the Holder following the
issuance of any Additional Registrable Securities or the issuance of any
securities convertible into, exchangeable for, or otherwise entitling the Holder
to acquire, Additional Registrable Securities, and in any event within 30 days
following such demand, the Company shall prepare and file with the SEC a new
Registration Statement on Form S-3 (or, if Form S-3 is not then available to the
Company, on such form of registration statement as is then available to effect a
registration for resale of the Additional Registrable Securities) covering the
resale of the Additional Registrable Securities in an amount equal to the number
of Additional Registrable Securities. Such Registration Statement also shall
cover, to the extent permitted by the 1933 Act and the rules promulgated
thereunder (including Rule 416), such indeterminate number of additional shares
of Common Stock resulting from stock splits, stock dividends or similar
transactions with respect to the Additional Registrable Securities. The
Registration Statement required by this Section 2(a)(ii) (and each amendment or
supplement thereto) shall be provided in accordance with Section 3(c) to the
Holder and its counsel prior to its filing or other submission. Nothing herein
shall limit the Company's obligations or the Holder's rights under Section 6(e)
of the Note, Section 10 of the Closing Warrant or Section 5 of the Redemption
Warrant.

            (iii) CERTAIN OTHER REGISTRATION STATEMENTS. If the Company proposes
to file with the SEC a registration statement (other than on Form S-8) relating
to securities other than the Registrable Securities or Additional Registrable
Securities prior to the deadline for filing such Registration Statement
hereunder, then on or before the date the Company files such other registration
statement with the SEC the Company shall file the Registration Statement
required by Section 2(a)(i) or 2(a)(ii), as the case may be, with the SEC.
Except as required pursuant to the Registration Rights Agreement, dated as of
September 16, 2002, by and among the Company and the parties named therein, or
the Registration Rights Agreement, dated as of September 17, 2002, by and among
the Company and the parties named therein, the Company shall not request
acceleration of effectiveness of such other

                                      -7-

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registration statement unless simultaneously therewith the Company requests
acceleration of effectiveness of the Registration Statement to the same date and
time as so requested for such other registration statement.

            (iv)  CERTAIN DISCLOSURES. If the Company proposes to include
disclosure in any Registration Statement to be filed with the SEC of the
circumstances under which the Holder acquired the Registrable Securities to be
offered pursuant to such Registration Statement, such disclosure shall include
statements to the effect that the securities being offered may include
Registrable Securities (1) issued upon conversion of, or in lieu of payment of
cash interest on, the Note, (2) issued upon exercise of the Closing Warrant or,
in case of redemption of the Note pursuant to Section 2(b) thereof, upon
exercise of the Redemption Warrant and (3) issued in exchange for, or otherwise
in respect of, the Note or the Warrants.

            (b)   EXPENSES. All expenses, other than underwriting discounts and
commissions and other fees and expenses of investment bankers and other than
brokerage commissions, incurred in connection with registrations, filing or
qualifications pursuant to this Agreement, including, without limitation, all
registration, listing and qualifications fees, printers and accounting fees and
the fees and disbursements of counsel for the Company, shall be borne by the
Company.

            (c)   EFFECTIVENESS.

            (i)   The Company shall use its best efforts to have each
Registration Statement declared effective as soon as practicable after it is
filed with the SEC. If (A) the Company fails to file with the SEC a Registration
Statement in accordance with all of the requirements of this Agreement on or
before the date by which the Company is required to file the Registration
Statement pursuant to Section 2(a)(i) above, (B) the Company fails to file with
the SEC the Registration Statement covering Additional Registrable Securities in
accordance with all of the requirements of this Agreement within 30 days
following demand of the Holder relating to the Additional Registrable Securities
to be covered thereby, (C) the Company fails to file with the SEC a request for
acceleration of effectiveness of a Registration Statement to a time and date not
more than 48 hours after the submission of such request, within three Trading
Days after the date the Company learns that no review of the Registration
Statement will be made by the staff of the SEC or that the staff of the SEC has
no further comments on the Registration Statement, as the case may be, (D) the
Registration Statement covering Registrable Securities is not declared effective
by the SEC within 75 days (or 105 days in case the SEC staff reviews such
Registration Statement) following the Closing Date, or the Registration
Statement covering additional Registrable Securities is not declared effective
by the SEC within 75 days (or 105 days in case the SEC staff reviews such
Registration Statement) following the date on which a Registration

                                      -8-

<PAGE>

Insufficiency Event occurs, or the Registration Statement covering Additional
Registrable Securities is not declared effective by the SEC within 75 days (or
105 days in case the SEC staff reviews such Registration Statement) following
demand of the Holder relating to the Additional Registrable Securities to be
covered thereby, (E) except as otherwise permitted by Section 2(c)(ii), after a
Registration Statement has been declared effective by the SEC sales cannot be
made pursuant to such Registration Statement or the related Prospectus for any
reason, including, without limitation, by reason of a stop order, misstatements
or omissions in such Registration Statement or Prospectus, or the Company's
failure to update such Registration Statement or Prospectus, excluding any such
inability to make sales that results from an untrue statement of a material fact
in such Registration Statement or Prospectus or omission to state a material
fact required to be stated in such Registration Statement or Prospectus in order
to make the statements therein not misleading, which misstatement or omission
was made by the Holder in written information it furnished to the Company
specifically for inclusion in such Registration Statement or Prospectus which
such information was substantially relied upon by the Company in preparation of
the Registration Statement or Prospectus or any amendment or supplement thereto,
unless the Company shall have failed timely to amend or supplement such
Registration Statement or Prospectus after the Holder shall have corrected such
misstatement or omission, or (F) the Common Stock generally or the Registrable
Securities (or Additional Registrable Securities after issuance) specifically
are not listed or included for quotation on the Nasdaq, the NYSE or the AMEX
(each an "Approved Market"), or trading of the Common Stock is suspended or
halted on the Approved Market which at the time constitutes the Principal Market
for the Common Stock (each of the events in the preceding clauses (A) through
(F) a "Compensation Event"), then the Company will make payments to the Holder
as partial liquidated damages for the minimum amount of damages to the Holder by
reason thereof, and not as a penalty, at the Compensation Rate (the
"Compensation Payments") on the sum of (x) the outstanding principal amount of,
and accrued interest on, the Note held at such time by the Holder plus (y) the
amount, if any, by which the product of (i) the average of the daily VWAPs for
all of the Trading Days during the particular portion of the Compensation Period
for which such computation is being made times (ii) the number of Warrant Shares
issuable upon exercise for cash of the unexercised portion of the Warrants held
at such time by the Holder exceeds the aggregate Purchase Price of the number of
Warrant Shares issuable upon exercise for cash of the unexercised portion of the
Warrants held at such time by the Holder, plus (z) the product of (1) the number
of outstanding Registrable Securities held at such time by the Holder times (2)
the greater of (i) the average of the daily VWAPs for all of the Trading Days in
the particular portion of the Compensation Period for which such computation is
being made and (ii) the Purchase Price of such Registrable Securities (in the
case of Registrable Securities issued upon exercise of the Warrants), the
Conversion Price of such Registrable Securities (in the case of Registrable
Securities issued upon conversion of the Note), the Interest Share Price

                                      -9-

<PAGE>

(in the case of Registrable Securities issued in lieu of payment of cash
interest on the Note) or the Computed Price used to compute that portion of the
Share Redemption Share Amount consisting of such shares (in the case of
Registrable Securities issued in a Share Redemption of the Note), in each such
case for each day on which any Compensation Event is continuing (the
"Compensation Period"). Each such payment shall be due and payable within five
days after the end of each calendar month of the Compensation Period until the
termination of the Compensation Period and within five days after such
termination. Such payments shall be in partial compensation to the Holder, and
shall not constitute the Holder's exclusive remedy for any Compensation Event;
provided, however, that if because of a particular Compensation Event the Holder
is successful in recovering on a claim for damages under this Agreement from
such Compensation Event, the amount of Compensation Payments previously paid by
the Company to the Holder with respect to such Compensation Event shall be
applied to reduce the amount of such recovery to the extent of such Compensation
Event. A particular Compensation Period shall terminate upon (v) the filing of
the applicable Registration Statement in the case of clauses (A) and (B) above;
(w) the effectiveness of the applicable Registration Statement in the case of
clauses (C) and (D) above; (x) the date sales can once again be made under the
Registration Statement in the case of clause (E) above, (y) listing or inclusion
and/or trading of the Common Stock on an Approved Market, as the case may be, in
the case of clause (F) above; and (z) in the case of the events described in
clauses (C), (D) or (E) above, the earlier termination of the Registration
Period (as defined in Section 3(a) below), and in each such case any
Compensation Period that commences by reason of the occurrence of such event
shall terminate if at the time no other Compensation Event is continuing. The
amounts payable as partial liquidated damages pursuant to this paragraph shall
be payable in lawful money of the United States. If the Company fails to pay any
liquidated damages pursuant to this Section in full within three days after the
date payable, the Company will pay interest thereon at a rate of 18% per annum
(or such lesser rate that is the highest rate permitted by applicable law) to
the Holder, accruing daily from the date such liquidated damages are due until
such amounts, plus all such interest thereon, are paid in full. Amounts payable
as partial liquidated damages hereunder shall cease when the Holder no longer
holds any Note, the Warrants, Registrable Securities or Additional Registrable
Securities.

            (ii)  For not more than ten consecutive Trading Days or for a total
of not more than 20 Trading Days in any period of 12 consecutive months, the
Company may suspend the use of the Registration Statement(s) that are effective
at such time because the Company determines to delay the disclosure of material
non-public information concerning the Company, if the disclosure of such
information at the time is not, in the good faith opinion of the Company, in the
best interests of the Company or would be unduly detrimental to the Company's
affairs (an "Allowed Delay"); provided, that the Company shall not later than
the date a suspension goes into effect (a) notify the Holder in writing of the
suspension of use of the

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<PAGE>

Registration Statement (but in no event, without the prior written consent of
the Holder, shall the Company disclose to the Holder any of the material
non-public information giving rise to an Allowed Delay), and (b) advise the
Holder in writing to cease all sales under the Registration Statement until the
end of the Allowed Delay. The Company shall notify the Holder on the date a
Registration Statement the use of which has been suspended under this Section
2(c)(ii) is once again available for use. If the Company shall have suspended
the use of the Registration Statement, then no period of Allowed Delay
subsequent to such suspension shall commence sooner than 30 days after the date
on which the Company notifies the Holder that such earlier suspension shall have
been lifted.

            (d)   OTHER REGISTRATION. If at any time or from time to time a new
Registration Statement is necessary or appropriate to afford the Holders the
rights and benefits intended to be provided to them by this Agreement, the
Company shall, upon request of any Holder, promptly prepare on the appropriate
SEC form, file with the SEC, and use its best efforts to obtain and maintain
effectiveness of, a new Registration Statement to the same extent as any other
Registration Statement provided for in this Agreement.

            3.    COMPANY OBLIGATIONS. The Company will use its best efforts to
effect the registration of the Registrable Securities and Additional Registrable
Securities at the times and for the periods specified in this Agreement. The
Company hereby covenants and agrees to:

            (a)   use its best efforts to cause such Registration Statement to
become effective and to remain continuously effective and available for use by
the Holders named therein as selling stockholders for a period (the
"Registration Period") that will terminate upon the earlier of (i) the date on
which all Registrable Securities or Additional Registrable Securities have been
sold (and the Note and the Warrants no longer remain outstanding) and (ii) the
date on which all Registrable Securities or Additional Registrable Securities,
as the case may be, that are issued or may be issued are eligible for sale by
the Holder pursuant to Rule 144(k) promulgated under the 1933 Act;

            (b)   prepare and file with the SEC such amendments, post-effective
amendments and prospectus supplements to the Registration Statement and the
Prospectus as may be necessary to keep the Registration Statement effective and
available for use by the Holders named therein as selling stockholders for the
period specified in Section 3(a) and to comply with the provisions of the 1933
Act and the 1934 Act with respect to the distribution of all Registrable
Securities and Additional Registrable Securities; provided that, at a time
reasonably, but not less than four Business Days, prior to the filing of a
Registration Statement or Prospectus, or any amendments or supplements thereto,
with the SEC the Company will furnish to the Holder copies of all documents
proposed to be filed, which documents will be subject to the comments, if any,
that the Holder provides to the Company reasonably

                                      -11-

<PAGE>

promptly after receipt of such documents; not later than two Business Days after
the Amendment Closing Date, file with the SEC a Current Report on Form 8-K that
includes copies of the Purchase Agreement Amendment and the exhibits thereto;
and not later than the Amendment Closing Date, file with the SEC a prospectus
supplement or amended Prospectus pursuant to Rule 424 under the 1933 Act that
includes all information relating to the Purchase Agreement Amendment and the
transactions contemplated thereby that is required to be disclosed in the
Prospectus;

            (c)   permit counsel designated by the Holder to review each
Registration Statement and Prospectus and all amendments and supplements thereto
no fewer than four Business Days (or as many Business Days as possible if SEC
rules do not allow such time for such review) prior to their filing with the SEC
and not file any document to which such counsel reasonably objects;

            (d)   furnish to the Holder and its legal counsel (i) promptly after
the same is prepared and publicly distributed, filed with the SEC, or received
by the Company, one copy of any Registration Statement and any amendment
thereto, each preliminary prospectus and Prospectus and each amendment or
supplement thereto, and each letter written by or on behalf of the Company to
the SEC or the staff of the SEC, and each item of correspondence from the SEC or
the staff of the SEC, in each case relating to such Registration Statement
(other than any portion of any thereof which contains information for which the
Company has sought confidential treatment), and (ii) within two Business Days
after the effective date of each Registration Statement and within two days
after any Prospectus or amendment or supplement thereto is prepared or filed
with the SEC, at least five copies of a Prospectus, including a preliminary
prospectus, and all amendments and supplements thereto, and such other documents
as the Holder may reasonably request in order to facilitate the disposition of
the Registrable Securities and Additional Registrable Securities owned by the
Holder, and thereafter promptly after the Holder from time to time requests,
such additional number of copies thereof as the Holder may request;

            (e)   in the event the Holder selects an underwriter for the
offering, enter into and perform its obligations under an underwriting
agreement, in usual and customary form, including, without limitation, customary
indemnification and contribution obligations, with the underwriter of such
offering;

            (f)   if the Holder is described in the Registration Statement as an
underwriter, the Company shall use its best efforts to furnish, on the effective
date of the Registration Statement and at periodic intervals thereafter from
time to time on request, (i) an opinion, dated as of such date, from outside
legal counsel representing the Company for purposes of such Registration
Statement, in form, scope and substance as is customarily given in an
underwritten public offering,

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addressed to the Holder and (ii) a letter, dated such date, from the Company's
independent certified public accountants in form and substance as is customarily
given by independent certified public accountants to underwriters in an
underwritten public offering, addressed to the Holder;

            (g)   use its best efforts to prevent the issuance of any stop order
or other suspension of effectiveness and, if such order is issued, use its best
efforts to obtain the withdrawal of any such order at the earliest possible
moment;

            (h)   furnish to the Holder at least five copies of the Registration
Statement and any post-effective amendment thereto, including financial
statements and schedules by reputable overnight courier within three Business
Days after the effective date thereof;

            (i)   use its commercially reasonable best efforts to register or
qualify the Registrable Securities or Additional Registrable Securities, as
applicable, for offer and sale under the securities or blue sky laws of such
jurisdictions requested by the Holder prior to the effective date with the SEC
of the applicable Registration Statement and do any and all other reasonable
acts or things necessary or advisable to enable the distribution in such
jurisdictions of the Registrable Securities or Additional Registrable Securities
covered by the Registration Statement; provided, however, that the Company shall
not be required in connection therewith or as a condition thereto to (a) qualify
to do business in any jurisdiction where it would not otherwise be required to
qualify but for this Section 3(i), (b) subject itself to general taxation in any
such jurisdiction, (c) file a general consent to service of process in any such
jurisdiction, or (d) make any change in its charter or bylaws, which in each
case the Board of Directors of the Company determines to be contrary to the best
interests of the Company and its shareholders.

            (j)   without limiting the Company's obligation under the
Transaction Documents to maintain the listing of the Common Stock on an Approved
Market, cause all Registrable Securities or Additional Registrable Securities
covered by a Registration Statement to be listed on each securities exchange,
interdealer quotation system or other market on which similar securities issued
by the Company are then listed;

            (k)   cooperate with the Holder to facilitate the timely preparation
and delivery of certificates representing Registrable Securities to be delivered
to a transferee pursuant to a Registration Statement, which certificates shall
be free, to the extent permitted by the Purchase Agreement, of all restrictive
legends, and to enable such Registrable Securities to be in such denominations
and registered in such names as the Holder may request;

                                      -13-

<PAGE>

            (l)   immediately notify the Holder at any time when a Prospectus
relating to the Registrable Securities or Additional Registrable Securities is
required to be delivered under the 1933 Act, upon discovery that, or upon the
happening of any event as a result of which, the Prospectus included in such
Registration Statement, as then in effect, includes an untrue statement of a
material fact or omits to state any material fact required to be stated therein
or necessary to make the statements therein, in the light of the circumstances
under which made, not misleading and promptly prepare and furnish to such holder
a reasonable number of copies of a supplement to or an amendment of such
Prospectus as may be necessary so that, as thereafter delivered to the
purchasers of such Registrable Securities or Additional Registrable Securities,
as applicable, such Prospectus shall not include an untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein not misleading in the light of the
circumstances then existing; and

            (m)   otherwise comply with all applicable rules and regulations of
the SEC under the 1933 Act and the 1934 Act, take such other actions as may be
reasonably necessary to facilitate the registration of the Registrable
Securities and Additional Registrable Securities, if applicable, hereunder; and
make available to its security holders, as soon as reasonably practicable, but
not later than the Availability Date, an earnings statement covering a period of
at least twelve months, beginning after the effective date of each Registration
Statement, which earnings statement shall satisfy the provisions of Section
11(a) of the 1933 Act. "Availability Date" means, with respect to a particular
Registration Statement, (1) the day on which the Company's Quarterly Report on
Form 10-Q for the fourth consecutive fiscal quarter following the fiscal quarter
that includes the effective date of such Registration Statement is due for
filing with the SEC (after giving effect to any extension permitted by Rule
12b-25 under the 1934 Act and claimed by the Company), in case such fourth
fiscal quarter is one of the first three fiscal quarters of the Company's fiscal
year, or (2) the day on which the Company's Annual Report on Form 10-K covering
a fiscal year that ends at the end of the fourth fiscal quarter following the
fiscal quarter that includes the effective date of such Registration Statement
is due for filing with the SEC (after giving effect to any extension permitted
by Rule 12b-25 under the 1934 Act and claimed by the Company) in case such
fourth fiscal quarter is the fourth fiscal quarter of the Company's fiscal year.

            4.    DUE DILIGENCE REVIEW; INFORMATION. The Company shall make
available, during normal business hours, for inspection and review by the
Holder, advisors to and representatives of the Holder (who may or may not be
affiliated with the Holder and who are reasonably acceptable to the Company),
and any underwriter participating in any disposition of Common Stock on behalf
of the Holder pursuant to the Registration Statement or amendments or
supplements thereto or any blue sky, NASD, or other filing, all financial and
other records, all

                                      -14-

<PAGE>

SEC Filings and other filings with the SEC, and all other corporate documents
and properties of the Company as may be reasonably necessary for the purpose of
establishing a due diligence defense under applicable securities laws and such
other reasonable purposes, and cause the Company's officers, directors and
employees, within a reasonable time period, to supply all such information
reasonably requested by the Holder or any such representative, advisor or
underwriter in connection with such Registration Statement (including, without
limitation, in response to all questions and other inquiries reasonably made or
submitted by any of them), prior to and from time to time after the filing and
effectiveness of the Registration Statement for the sole purpose of enabling the
Holder and such representatives, advisors and underwriters and their respective
accountants and attorneys to conduct initial and ongoing due diligence with
respect to the Company and the accuracy of the Registration Statement.

            The above to the contrary notwithstanding, the Company shall not
disclose material nonpublic information to the Holder, or to advisors to or
representatives of the Holder, unless prior to disclosure of such information
the Company identifies such information as being material nonpublic information
and provides the Holder, such advisors and representatives with the opportunity
to accept or refuse to accept such material nonpublic information for review.
The Company may, as a condition to disclosing any material nonpublic information
hereunder, require the Holder's advisors and representatives to enter into a
confidentiality agreement (including an agreement with such advisors and
representatives prohibiting them from trading in Common Stock during such period
of time as they are in possession of material nonpublic information) in form
reasonably satisfactory to the Company and the Holder.

            5.    OBLIGATIONS OF THE HOLDER.

            (a)   The Holder shall furnish in writing to the Company such
information regarding itself, the Registrable Securities or Additional
Registrable Securities, as applicable, held by it and the intended method of
disposition of the Registrable Securities or Additional Registrable Securities,
as applicable, held by it, as shall be required by the 1933 Act to effect the
registration of such Registrable Securities or Additional Registrable
Securities, as applicable, and shall execute such documents in connection with
such registration as the Company may reasonably request. At least five Business
Days prior to the first anticipated filing date of any Registration Statement
(or such shorter period as may be agreed to by the Holder), the Company shall
notify the Holder of the information the Company requires from the Holder if the
Holder's Registrable Securities or Additional Registrable Securities are to be
included in the Registration Statement.

            (b)   The Holder, by its acceptance of the Registrable Securities
and Additional Registrable Securities, if any, agrees to cooperate with the
Company as

                                      -15-

<PAGE>

reasonably requested by the Company in connection with the preparation and
filing of a Registration Statement hereunder, unless the Holder has notified the
Company in writing of its election to exclude all of its Registrable Securities
or Additional Registrable Securities, as applicable, from the Registration
Statement.

            (c)   The Holder agrees that, upon receipt of any notice from the
Company of the happening of any event rendering a Registration Statement no
longer effective or available for use by the Holder, the Holder will immediately
discontinue disposition of Registrable Securities or Additional Registrable
Securities pursuant to the Registration Statement covering such Registrable
Securities or Additional Registrable Securities, until the Holder's receipt of
the copies of the supplemented or amended Prospectus filed with the SEC and
declared effective and, if so directed by the Company, the Holder shall deliver
to the Company (at the expense of the Company) or destroy all copies in the
Holder's possession, or instruct its agents or other representatives to deliver
to the Company (at the Company's expense) or destroy all copies in such agents'
or other representatives' possession, in either case of the Prospectus covering
the Registrable Securities or Additional Registrable Securities, as applicable,
current at the time of receipt of such notice.

            6.    INDEMNIFICATION.

            (a)   INDEMNIFICATION BY COMPANY. The Company agrees to indemnify
and hold harmless, to the fullest extent permitted by law, the Holder, each
investment advisor and investment sub-advisor of the Holder and each of their
respective officers, directors, partners, members and employees and each person
who controls the Holder (within the meaning of the 1933 Act) against all losses,
claims, damages, liabilities, costs (including, without limitation, reasonable
attorney's fees) and expenses imposed on such person caused by (i) any untrue or
alleged untrue statement of a material fact contained in any Registration
Statement, Prospectus or any preliminary prospectus or any amendment or
supplement thereto or any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, except insofar as the same are based upon any
information furnished in writing to the Company by the Holder, expressly for use
therein, or (ii) any violation by the Company of any federal, state or common
law, rule or regulation applicable to the Company in connection with any
Registration Statement, Prospectus or any preliminary prospectus, or any
amendment or supplement thereto, and shall reimburse in accordance with
subparagraph (c) below, each of the foregoing persons for any legal and any
other expenses reasonably incurred in connection with investigating or defending
any such claims. The foregoing is subject to the condition that, insofar as the
foregoing indemnities relate to any untrue statement, alleged untrue statement,
omission or alleged omission made in any preliminary prospectus or Prospectus
that is eliminated or remedied in any Prospectus or

                                      -16-

<PAGE>

amendment or supplement thereto, the above indemnity obligations of the Company
shall not inure to the benefit of any indemnified party if a copy of such
corrected Prospectus or amendment or supplement thereto had been timely provided
to such indemnified party and was not sent or given by such indemnified party at
or prior to the time such action was required of such indemnified party by the
1933 Act and if delivery of such Prospectus or amendment or supplement thereto
would have eliminated (or been a sufficient defense to) any liability of such
indemnified party with respect to such statement or omission. Indemnity under
this Section 5(a) shall remain in full force and effect regardless of any
investigation made by or on behalf of any indemnified party and shall survive
the transfer of the Registrable Securities and Additional Registrable
Securities.

            (b)   INDEMNIFICATION BY HOLDER. In connection with any registration
pursuant to the terms of this Agreement, the Holder will furnish to the Company
in writing such information as required by the 1933 Act concerning the Holder or
the proposed manner of distribution for use in connection with any Registration
Statement or Prospectus and agrees to indemnify and hold harmless, to the
fullest extent permitted by law, the Company, its directors, officers, and each
person who controls the Company (within the meaning of the 1933 Act) against any
losses, claims, damages, liabilities and expense (including reasonable
attorney's fees) resulting from any untrue statement of a material fact in the
Registration Statement or Prospectus or preliminary prospectus or amendment or
supplement thereto or any omission of a material fact required to be stated in
the Registration Statement or Prospectus or preliminary prospectus or amendment
or supplement thereto necessary to make the statements therein not misleading,
to the extent, but only to the extent that such untrue statement is contained or
such omission is made in any information about the Holder furnished in writing
by such Holder to the Company specifically for inclusion in such Registration
Statement or Prospectus or amendment or supplement thereto and that such
information was substantially relied upon by the Company in preparation of the
Registration Statement or Prospectus or any amendment or supplement thereto. In
no event shall the liability of the Holder be greater in amount than the dollar
amount of the proceeds (net of the cost of the Registrable Securities and
Additional Registrable Securities sold and all expenses paid by the Holder and
not reimbursed by the Company and the amount of any damages the Holder has
otherwise been required to pay by reason of such untrue statement or omission)
received by the Holder upon the sale of the Registrable Securities or Additional
Registrable Securities included in the Registration Statement giving rise to
such indemnification obligation.

            (c)   CONDUCT OF INDEMNIFICATION PROCEEDINGS. Any person entitled to
indemnification hereunder shall (i) give prompt notice to the indemnifying party
of any claim with respect to which it seeks indemnification, (ii) permit such
indemnifying party to assume the defense of such claim with counsel reasonably
satisfactory to the indemnified party and (iii) by notice to the

                                      -17-

<PAGE>

indemnifying party, require the indemnifying party to assume the defense of such
claim with counsel reasonably satisfactory to the indemnified party; provided,
however, that any person entitled to indemnification hereunder shall have the
right to employ separate counsel and to participate in the defense of such
claim, but the fees and expenses of such counsel shall be at the expense of such
person unless (a) the indemnifying party has agreed to pay such fees or
expenses, or (b) the indemnifying party shall have failed to assume the defense
of such claim and employ counsel reasonably satisfactory to such person or (c)
in the reasonable judgment of any such person, based upon written advice of its
counsel, a conflict of interest exists between such person and the indemnifying
party with respect to such claims (in which case, if the person notifies the
indemnifying party in writing that such person elects to employ separate counsel
at the expense of the indemnifying party, the indemnifying party shall not have
the right to assume the defense of such claim on behalf of such person); and
provided, however, further, that the failure of any indemnified party to give
notice as provided herein shall not relieve the indemnifying party of its
obligations hereunder, except to the extent that such failure to give notice
shall materially adversely affect the indemnifying party in the defense of any
such claim or litigation. It is understood that the indemnifying party shall
not, in connection with any proceeding in the same jurisdiction, be liable for
fees or expenses of more than one separate firm of attorneys at any time for all
such indemnified parties. No indemnifying party will, except with the consent of
each indemnified party, consent to entry of any judgment or enter into any
settlement that does not include as an unconditional term thereof the giving by
the claimant or plaintiff to such indemnified party of a release from all
liability in respect of such claim or litigation.

            (d)   CONTRIBUTION. If for any reason the indemnification provided
for in the preceding paragraphs (a) and (b) is unavailable to an indemnified
party or insufficient to hold it harmless, other than as expressly specified
therein, then the indemnifying party shall contribute to the amount paid or
payable by the indemnified party as a result of such loss, claim, damage or
liability in such proportion as is appropriate to reflect the relative fault of
the indemnified party and the indemnifying party, as well as any other relevant
equitable considerations. No person guilty of fraudulent misrepresentation
within the meaning of Section 11(f) of the 1933 Act shall be entitled to
contribution from any person not guilty of such fraudulent misrepresentation. In
no event shall the contribution obligation of a holder of Registrable Securities
or Additional Registrable Securities be greater in amount than the dollar amount
of the proceeds (net of the cost of the Registrable Securities or Additional
Registrable Securities sold and all expenses paid by such holder and not
reimbursed by the Company and the amount of any damages such holder has
otherwise been required to pay by reason of such untrue or alleged untrue
statement or omission or alleged omission) received by it upon the sale of the
Registrable Securities or Additional Registrable Securities giving rise to such
contribution obligation.

                                      -18-

<PAGE>

            7.    MISCELLANEOUS.

            (a)   AMENDMENTS AND WAIVERS. Prior to the date the Registration
Statement contemplated by Section 2(a)(i) is first ordered effective by the SEC
or at any time thereafter during the Registration Period that the Registration
Statement or Prospectus shall not be effective or available for use by the
Holder to sell Registrable Securities, this Agreement may be amended only by a
writing signed by the Company and the Holder. Except as provided in the
immediately preceding sentence, the Company may take any action herein
prohibited, or omit to perform any act herein required to be performed by it, in
any such case after the Registration Statement covering the Initial Registrable
Securities Amount is declared effective by the SEC only if the Company shall
have obtained the written consent to such amendment, action or omission to act,
of the Holder and holders under the Other Registration Rights Agreements who
hold, directly or indirectly, at least 66 2/3% of the aggregate number of
Registrable Securities and Additional Registrable Securities (as defined herein
or in the Other Registration Rights Agreements) held by the Holder and such
other holders.

            (b)   NOTICES. All notices and other communications provided for or
permitted hereunder shall be made as set forth in Section 8.4 of the Purchase
Agreement or, in the case of any Holder other than the Investor, to such Holders
address set forth in the instrument signed by such Holder pursuant to Section
7(c) or such other address as provided by such Holder by notice to the Company.

            (c)   ASSIGNMENTS AND TRANSFERS BY HOLDER. This Agreement and the
rights and obligations of the Holder hereunder may be assigned or transferred in
whole to any transferee or assignee of the Note, the Warrants, the Registrable
Securities or the Additional Registrable Securities or in part to any transferee
or assignee of any portion thereof, except as otherwise set forth herein. The
Holder may make such assignment or transfer to any transferee or assignee of the
Note, the Warrants, the Registrable Securities or the Additional Registrable
Securities; provided, that (i) such transfer is made expressly subject to this
Agreement and the transferee agrees in writing to be bound by the terms and
conditions hereof, and (ii) the Company is provided with written notice of such
assignment.

            (d)   ASSIGNMENTS AND TRANSFERS BY THE COMPANY. This Agreement may
not be assigned by the Company without the prior written consent of the Holder
but, in any case of any successor-in-interest to the Company or any Person other
than the Company who is an issuer of Registrable Securities or Additional
Registrable Securities, such successor-in-interest or other issuer, shall
assume, jointly and severally with the Company, the rights and duties of the
Company hereunder, in the event of a merger or consolidation of the Company with
or into another corporation or the sale of all or substantially all of the
Company's

                                      -19-

<PAGE>

assets (and it shall be a condition to any such merger, consolidation or sale
that such successor-in-interest or other issuer assume in writing all
obligations hereunder jointly and severally with the Company as provided herein
and in the Note and the Warrants).

            (e)   BENEFITS OF THE AGREEMENT. The terms and conditions of this
Agreement shall inure to the benefit of and be binding upon the respective
permitted successors and assigns of the parties. Nothing in this Agreement,
express or implied, is intended to confer upon any party other than the parties
hereto or their respective permitted successors and assigns any rights,
remedies, obligations, or liabilities under or by reason of this Agreement,
except as expressly provided in this Agreement.

            (f)   COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

            (g)   TITLES AND SUBTITLES. The titles and subtitles used in this
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

            (h)   SEVERABILITY. If one or more provisions of this Agreement are
held to be unenforceable under applicable law, such provision shall be excluded
from this Agreement and the balance of this Agreement shall be interpreted as if
such provision were so excluded and shall be enforceable in accordance with its
terms to the fullest extent permitted by law.

            (i)   FURTHER ASSURANCES. The parties shall execute and deliver all
such further instruments and documents and take all such other actions as may
reasonably be required to carry out the transactions contemplated hereby and to
evidence the fulfillment of the agreements herein contained.

            (j)   ENTIRE AGREEMENT. This Agreement, together with the Purchase
Agreement, the Note and the Warrants and documents contemplated thereby, is
intended by the parties as a final expression of their agreement and intended to
be a complete and exclusive statement of the agreement and understanding of the
parties hereto in respect of the subject matter contained herein. This
Agreement, together with the Purchase Agreement, the Note and the Warrants and
documents contemplated thereby, supersedes all prior agreements and
understandings between the parties with respect to such subject matter.

            (k)   APPLICABLE LAW. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of New York without regard
to principles of conflicts of law.

                                      -20-

<PAGE>

                            [Signature Page Follows]

                                      -21-

<PAGE>

      IN WITNESS WHEREOF, the parties have caused this Registration Rights
Agreement to be duly executed by their respective officers or other
representatives thereunto duly authorized as of the date first written above.

                                   ZIX CORPORATION

                                   By:
                                        _______________________________
                                        Name:
                                        Title:

                                  [                                   ]

                                   By:
                                        _______________________________
                                        Name:
                                        Title:

                                      -22-