SECURITIES PURCHASE AGREEMENT

Exhibit 4.1

SECURITIES PURCHASE AGREEMENT

     This Securities Purchase Agreement (this “ Agreement ”) is made and entered into as of August 9, 2005 (the “ Execution Date ”), by and among Zix Corporation, a Texas corporation (the “ Company ”), and each of the purchasers listed on Schedule A attached hereto (collectively, the “ Purchasers ” and individually, a “ Purchaser ”).

RECITALS

     WHEREAS, the Company desires to sell to the Purchasers, and the Purchasers desire to purchase from the Company, up to an aggregate of 10,503,862 units (each a “ Unit ”), each Unit consisting of one share of common stock, par value $.01 per share, of the Company (“ Common Stock ”) and a five year warrant (a “ Warrant ”) to purchase one-third of one share of Common Stock, on the terms and conditions set forth in this Agreement; and

     WHEREAS, the Company and each Purchaser are executing and delivering this Agreement in reliance upon an exemption from securities registration afforded by Regulation D (“ Regulation D ”) as promulgated by the Securities and Exchange Commission (the “ SEC ”) under the Securities Act of 1933, as amended (the “ Securities Act ”).

     NOW, THEREFORE, in consideration of the foregoing, the mutual promises hereinafter set forth, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

      1.  AGREEMENT TO PURCHASE AND SELL STOCK .

         (a)  Company Authorization . The Company’s Board of Directors has authorized the issuance and sale, pursuant to the terms and conditions of this Agreement, of up to 10,503,862 shares of Common Stock (the “ Purchased Shares ”) and up to 3,466,274 Warrants, substantially in the form attached hereto as Exhibit A . Each Warrant shall be exercisable to purchase the number of shares of Common Stock set forth thereon at a price of $3.04 per share of Common Stock (the “ Purchased Warrants ” and together with the Purchased Shares, the “ Purchased Securities ”). Subject to their terms and conditions, the Purchased Warrants shall be exercisable at any time and from time to time from and after the six-month anniversary of the Closing Date through and including August 9, 2010.

         (b)  Agreement to Purchase and Sell Securities .

               (i) Subject to the terms and conditions of this Agreement, each Purchaser, severally and not jointly, agrees to purchase, and the Company agrees to sell to each Purchaser, at the Closing (as defined below), that number of Units (including the Firm Units and Excess Units, each as defined below) set forth opposite such Purchaser’s name on Schedule A attached hereto. The purchase price of each Unit shall be $2.50 (the “ Per Unit Price ”), except in the case of each Unit purchased by a director or officer of the Company which shall be $2.99 (the “ Insider Per Unit Price ”) and each shall be payable as hereafter set forth.

               (ii) Notwithstanding anything to the contrary in this Agreement, on the Closing Date, no more than 6,302,318 Units representing 6,302,318 shares of Common Stock (the “ Firm Shares ”) and associated Warrants (the “Firm Warrants” , and together with the Firm Shares, the “Firm Units” ) shall be issued to the Purchasers prior to the Company obtaining shareholder approval to issue to the Purchasers the shares of Common Stock in excess of the Firm Units in accordance with the requirements of NASDAQ Rule 4350(i) and Section 5(d) hereto (the “ Shareholder Approval ”). Prior to obtaining the Shareholder Approval, the Units to be purchased by the Purchasers (including the Warrants thereto) representing Purchased Shares in excess of the Firm Units (the “ Excess Units ”) shall not be issued to the Purchasers and instead the proceeds in respect of such Excess Units (the “ Excess Funds ”) shall be deposited into escrow, in accordance with the terms of an escrow agreement, substantially in the form of Exhibit D hereto (the “ Escrow Agreement ”). The Excess Funds shall accrue interest from and including the day following the Closing Date to and excluding the date of release in accordance with the terms of the Escrow Agreement at a rate of 7.0% per annum (computed on the basis of a 365-day year). If the Company obtains the Shareholder Approval prior to the Shareholder Approval Date (as defined below), the Excess Funds shall be released to the Company in accordance with the Escrow Agreement, and the Excess Units shall be issued to each of the Purchasers in the amounts set forth on Schedule A hereto, along with such Purchaser’s pro rata share of accrued interest on the Excess Funds to such date, which shall be payable in cash. If the Company does not obtain the Shareholder Approval prior to the Shareholder Approval Date (as defined below), the Excess Funds shall be returned to each of the Purchasers in accordance with the terms of the Escrow Agreement, along with such Purchaser’s pro rata share of accrued interest on the Excess Funds to such date. If the Excess Funds accrue earnings or interest in escrow at a rate less than the rate required by this Section 1(b)(ii) , the Company shall promptly pay to the Purchasers any shortfall amount.

         (c)  Use of Proceeds . The Company intends to use the net proceeds from the sale of the Purchased Securities for working capital and general corporate purposes as determined by the Company from time to time.

         (d)  Obligations Several, Not Joint . The obligations of each Purchaser under this Agreement are several and not joint with respect to the obligations of any other Purchaser, and no Purchaser shall be responsible in any way for the performance of the obligations of any other Purchaser under this Agreement. The decision of each of the Purchasers to purchase the Purchased Securities pursuant to this Agreement has been made by such Purchaser independently of any other Purchaser. Nothing contained herein, and no action taken by any Purchaser pursuant hereto, shall be deemed to constitute the Purchasers as a partnership, an association, a joint venture or any other kind of entity, or create a presumption that the Purchasers are in any way acting in concert or as a group with respect to such obligations or the transactions contemplated by this Agreement. Each Purchaser shall be entitled to independently protect and enforce such Purchaser’s rights, including, without limitation, the rights arising out of this Agreement, and it shall not be necessary for any other Purchaser to be joined as an additional party in any proceeding for such purpose.

      2.  CLOSING . The purchase and sale of the Purchased Securities shall take place at the offices of Baker Botts L.L.P., 2001 Ross Avenue, Dallas, Texas 75201, at 2:00 p.m. Dallas, Texas time, on August 9, 2005, or at such other time and place as the Company and Purchasers

representing a majority of the Purchased Securities to be purchased, mutually agree upon (which time and place are referred to in this Agreement as the “ Closing ”). At the Closing, against delivery of full payment for the Purchased Securities sold hereunder by wire transfer of immediately available funds in accordance with the Company’s instructions; the Company shall issue and deliver to each Purchaser (i) one or more stock certificates registered in the name of each Purchaser (or in such nominee name(s) as designated by such Purchaser in the Stock Certificate and Warrant Questionnaire, attached hereto as Appendix I (the “ Stock Certificate Questionnaire ”), representing the number of Firm Shares set forth opposite the appropriate Purchaser’s name on Schedule A hereto, and bearing the legend set forth in Section 4(k)(i) herein and (ii) the number of Firm Warrants set forth opposite the appropriate Purchaser’s name on Schedule A hereto, and bearing the legend set forth in Section 4(k)(ii) ; provided, however , that the Company may furnish to each Purchaser a facsimile copy of the warrant representing the Firm Warrant and of the stock certificate(s) representing the Firm Shares purchased by such Purchaser no later than the next Business Day following the Closing Date, with the original warrant and original stock certificate(s) to be delivered to such Purchaser by overnight courier no later than the third (3rd) Business Day following the Closing Date. Closing documents, other than the warrants representing the Firm Warrants and the stock certificates representing the Firm Shares, may be delivered by facsimile on the Closing Date, with original signature pages subsequently sent by overnight courier.

     For purposes of this Agreement, “ Closing Date ” means the date of the Closing, and “ Business Day ” means any day except Saturday, Sunday and any day which shall be a federal legal holiday or a day on which banking institutions in the State of New York are authorized or required by law or other governmental action to close.

      3.  REPRESENTATIONS, WARRANTIES AND CERTAIN AGREEMENTS OF THE COMPANY . The Company hereby represents and warrants to each Purchaser that, except as set forth in the SEC Documents (as defined below) and in the Disclosure Letter attached hereto as Exhibit B (the “ Disclosure Letter ”):

         (a)  Organization Good Standing and Qualification . The Company is a corporation duly organized, validly existing and in good standing under the laws of the State of Texas and has all corporate power and authority required to (i) own, operate and occupy its properties and to carry on its business as presently conducted and (ii) enter into this Agreement and the other agreements, instruments and documents contemplated hereby, and to consummate the transactions contemplated hereby and thereby. The Company is qualified to do business and is in good standing in each jurisdiction in which the failure to so qualify would have a Material Adverse Effect. As used in this Agreement, “ Material Adverse Effect ” means a material adverse effect on, or a material adverse change in, the business, operations, financial condition, results of operations, assets or liabilities of the Company and the Subsidiaries (as defined below), taken as a whole.

         (b)  Capitalization . The capitalization of the Company is as follows:

               (i) The authorized capital stock of the Company consists of 175,000,000 shares of Common Stock, $.01 par value per share, and 10,000,000 shares of preferred stock, par value $1.00 per share (“ Preferred Stock ”).

               (ii) As of June 30, 2005, the issued and outstanding capital stock of the Company consisted of 32,424,929 shares of Common Stock and no shares of Preferred Stock. The shares of issued and outstanding capital stock of the Company have been duly authorized and validly issued, are fully paid and nonassessable and have not been issued in violation of or are not otherwise subject to any preemptive or other similar rights.

               (iii) As of June 30, 2005, the Company had 10,110,617 shares of Common Stock reserved for issuance upon exercise of options granted under the Company’s stock option plans.

               (iv) As of June 30, 2005, the Company had outstanding options for 8,211,325 shares of Common Stock.

               (v) As of June 30, 2005, the Company had 3,755,370 issued and outstanding warrants for the purchase of shares of Common Stock.

         With the exception of the foregoing in this Section 3(b) , there are no outstanding subscriptions, options, warrants, convertible or exchangeable securities or other rights to purchase shares of Common Stock or other securities of the Company, or rights that would trigger any anti-dilution or similar adjustments to any securities of the Company, granted to or by the Company, and there are no commitments, plans or arrangements to issue any shares of Common Stock or any security convertible into or exchangeable for Common Stock.

         (c)  Subsidiaries . Except for the Company’s subsidiaries listed in the SEC documents (the “ Subsidiaries ”), the Company does not own any capital stock of, assets comprising the business of, obligations of, or any other interest (including any equity or partnership interest) in, any person or entity. The Company owns, directly or indirectly, all of the issued and outstanding shares of stock in each of the Subsidiaries. Each of the Subsidiaries is duly organized and validly existing in good standing under the laws of its respective state of incorporation. Each of the Subsidiaries has full power and authority to own, operate and occupy its properties and to conduct its business as presently conducted and is registered or qualified to do business and in good standing in each jurisdiction in which it owns or leases property or transacts business and where the failure to be so qualified would have a Material Adverse Effect.

         (d)  Due Authorization . All corporate actions on the part of the Company necessary for the authorization, execution, delivery and performance of all obligations of the Company under this Agreement, including the authorization, issuance, reservation for issuance and delivery of all the Purchased Securities being sold under this Agreement and the Common Stock issuable upon exercise of the Purchased Warrants (the “ Warrant Shares ”), have been taken and no further consent or authorization of the Company, the Company’s board of directors (the “ Board of Directors ”) or the Company’s stockholders is required (other than the Shareholder Approval), and this Agreement constitutes the legal, valid and binding obligation of the Company, enforceable against the Company in accordance with its terms, except (i) as may be limited by (1) applicable bankruptcy, insolvency, reorganization or other laws of general application relating to or affecting the enforcement of creditors’ rights generally and (2) the effect of rules of law governing the availability of equitable remedies and (ii) as rights to indemnity or contribution may be limited under federal or state securities laws or by principles of public policy thereunder.

         (e)  Valid Issuance of the Purchased Securities .

               (i)  Purchased Shares . The Purchased Shares have been duly authorized and, when issued and delivered to each Purchaser against payment therefor in accordance with the terms of this Agreement, will be validly issued, fully paid and non-assessable and will be free and clear from all liens, claims and encumbrances with respect to the issuance of such Purchased Shares and will not be subject to any pre-emptive rights or similar rights.

               (ii)  Purchased Warrants . The Purchased Warrants to be issued pursuant to this Agreement have been duly authorized and, when issued and delivered to each Purchaser against payment therefor in accordance with the terms of this Agreement, will be validly issued and will be free and clear from all liens, claims and encumbrances with respect to the issuance of such Purchased Warrants and will not be subject to any pre-emptive rights or similar rights.

               (iii)  Warrant Shares . The issuance of the Warrant Shares issued or issuable from time to time upon the exercise of the Purchased Warrants have been, and at all times prior to such exercise, will be, duly authorized and duly reserved for issuance upon such exercise and payment of the exercise price of the Purchased Warrants and, when issued and delivered to each Purchaser upon exercise against payment therefor in accordance with the terms of the Warrant, will be validly issued, fully paid and non-assessable and will be free and clear from all liens, claims and encumbrances with respect to the issuance of such Warrant Shares and will not be subject to any pre-emptive rights or similar rights.

         (f)  Compliance with Securities Laws . Subject to the accuracy of the representations made by the Purchasers in Section 4 hereof, the Purchased Securities will be issued and sold to the Purchasers in compliance with (i) the exemption in Rule 506 of Regulation D promulgated under the Securities Act from the registration and prospectus delivery requirements of the Securities Act and (ii) applicable exemptions from the registration and qualification requirements of all applicable securities laws of the states of the United States.

         (g)  Governmental Consents . No consent, approval, order or authorization of, or registration, qualification, designation, declaration or filing with, or notice to, any federal, state or local governmental authority or self regulatory agency on the part of the Company is required in connection with the issuance and sale of the Purchased Securities to the Purchasers by the Company or the consummation of the other transactions contemplated by this Agreement, except (i) such filings as have been made prior to the date hereof, (ii) the filings under applicable securities laws required to comply with the Company’s registration obligations under Section 5(a) of this Agreement and (iii) such additional post-Closing filings as may be required to comply with applicable state and federal securities laws, including, but not limited to, the filing of a Form D relating to the sale of the Purchased Securities pursuant to Regulation D.

         (h)  Non-Contravention . Assuming the accuracy of the representations and warranties made by the Purchasers in Section 4 hereof, the execution, delivery and performance of this Agreement by the Company, and the consummation by the Company of the transactions contemplated hereby (including the issuance of the Purchased Securities and the Warrant Shares), do not: (i) contravene or conflict with the articles of incorporation, as amended (the “ Articles of Incorporation ”), or bylaws, as amended (the “ Bylaws ”), of the Company or of any Subsidiary; (ii) constitute a violation of any provision of any federal, state, local or foreign law, rule, regulation, order or decree applicable to the Company or any Subsidiary; or (iii) constitute a default (with or without the passage of time or giving of notice or both) or require any consent under, give rise to any right of termination, cancellation or acceleration of, or result in the creation or imposition of any lien, claim or encumbrance on any asset of the Company or the Subsidiaries under, any material contract to which the Company or the Subsidiaries is a party or any permit, license or similar right relating to the Company or the Subsidiaries or by which the Company or the Subsidiaries may be bound or affected, except in the case of clauses (ii) and (iii), for such violations, breaches or defaults as would not be reasonably likely to have a Material Adverse Effect.

         (i)  Litigation . Except as set forth in the SEC Documents, there is no action, suit, proceeding, claim, arbitration or investigation (“ Action ”) pending or, to the Company’s knowledge, threatened: (i) against the Company or any Subsidiary, their properties or assets, or any officer, director or employee of the Company or any Subsidiary in connection with such officer’s, director’s or employee’s relationship with, or actions taken on behalf of, the Company or any Subsidiary, that would be reasonably likely to have a Material Adverse Effect, or (ii) that seeks to prevent, enjoin, alter, challenge or delay the transactions contemplated by this Agreement. The Company is not a party to, nor subject to the provisions of, any order, writ, injunction, judgment or decree of any court or government agency or instrumentality that would reasonably be expected to prevent, enjoin, alter, challenge or delay the consummation of the transactions contemplated by this Agreement or would be reasonably likely to have a Material Adverse Effect. The SEC has not issued any stop order or other order suspending the effectiveness of any registration statement filed by the Company under the Securities Act or the Securities Exchange Act of 1934, as amended ( the “ Exchange Act ”).

         (j)  Compliance with Law and Charter Documents . The Company is not in violation or default of any provisions of the Articles of Incorporation or the Bylaws. The Company is currently in compliance with all applicable statutes, laws, rules, regulations and orders of the United States of America and all states thereof, foreign countries and other governmental bodies and agencies having jurisdiction over the Company’s business or properties, except for any instance of non-compliance that has not had, and would not reasonably be expected to have, a Material Adverse Effect. Neither the Company nor any Subsidiary is in default (and there exists no condition which, with or without the passage of time or giving of notice or both, would constitute a default) in any material respect in the performance of any bond, debenture, note or any other evidence of indebtedness in any indenture, mortgage, deed of trust or any other material agreement or instrument to which the Company or any Subsidiary is a party or by which the Company or any Subsidiary is bound or by which the properties of the Company or any Subsidiary is bound, which default would be reasonably likely to have a Material Adverse Effect or which would be reasonably likely to have a Material Adverse Effect on the transactions contemplated by this Agreement.

         (k)  Material Non-Public Information . The Company has not provided, and will not provide, to the Purchasers any material non-public information other than information related to the transactions contemplated by this Agreement, all of which information shall be disclosed by the Company pursuant to Section 9(m) hereof.

         (l)  SEC Documents .

               (1)  Reports . The Company has filed in a timely manner all reports, schedules, forms, statements and other documents required to be filed by it with the Securities and Exchange Commission (the “ SEC ”) pursuant to the reporting requirements of the Exchange Act and the rules and regulations promulgated thereunder. The Company has made available to the Purchasers prior to the date hereof copies of its Annual Report on Form 10-K for the fiscal year ended December 31, 2004, as amended (the “ Form 10-K ”), its quarterly report on Form 10-Q for the fiscal quarter ended March 31, 2005 (the “ Form 10-Q ”), and any Current Report on Form 8-K for events occurring since December 31, 2004 (“ Form 8-Ks ”) filed or furnished by the Company with the SEC (the Form 10-K, the Form 10-Q and the Form 8-Ks are collectively referred to herein as the “ SEC Documents ”). Each of the SEC Documents, as of the respective dates thereof (or, if amended or superseded by a filing or submission, as the case may be, prior to the Closing Date, then on the date of such filing or submission, as the case may be), (1) did not contain any untrue statement of a material fact nor omit to state a material fact necessary in order to make the statements made therein, in light of the circumstances under which they were made, not misleading and (2) complied in all material respects with the requirements of the Exchange Act and the rules and regulations of the SEC promulgated thereunder applicable to such SEC Document.

               (2)  Sarbanes-Oxley . The Chief Executive Officer and the Chief Financial Officer of the Company have signed, and the Company has furnished to the SEC, all certifications required by Sections 302 and 906 of the Sarbanes-Oxley Act of 2002. Such certifications contain no qualifications or exceptions to the matters certified therein (other than such qualifications or exceptions that are permitted under the Exchange Act and the rules promulgated thereunder) and have not been modified or withdrawn; and neither the Company nor any of its officers has received notice from any governmental entity questioning or challenging the accuracy, completeness, form or manner of filing or submission of such certifications. Without limiting the foregoing, the Company is in compliance with any applicable requirements of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated thereunder, as amended, that are currently in effect.

               (3)  Financial Statements . The consolidated financial statements of the Company included in the SEC Documents (1) comply as to form in all material respects with the rules and regulations of the SEC with respect thereto as were in effect at the time of filing and (2) present fairly, in all material respects, in accordance with United States generally accepted accounting principles (“ GAAP ”), consistently applied, the consolidated financial position of the Company as of the dates indicated therein, and the consolidated results of its operations and cash flows for the periods therein specified, subject, in the case of unaudited consolidated financial statements for interim periods, to normal, immaterial year-end audit adjustments.

         (m)  Absence of Certain Changes Since the Balance Sheet Date . Except as disclosed in the SEC Documents, since the filing of the Company’s most recent Form 10-K with the SEC, the business and operations of the Company and the Subsidiaries have been conducted in the ordinary course consistent with past practice, and there has not been:

               (i) any declaration, setting aside or payment of any dividend or other distribution of the assets of the Company with respect to any shares of capital stock of the Company or any repurchase, redemption or other acquisition by the Company or any Subsidiary of the Company of any outstanding shares of the Company’s capital stock;

               (ii) any damage, destruction or loss to the Company’s or any Subsidiary’s business or assets, whether or not covered by insurance, except for such occurrences, individually and collectively, that have not had, and would not reasonably be expected to have, a Material Adverse Effect;

               (iii) any waiver by the Company or any Subsidiary of a valuable right or of a material debt owed to it, except for such waivers, individually and collectively, that have not had, and would not reasonably be expected to have, a Material Adverse Effect;

               (iv) any material change or amendment to, or any waiver of any material right under a material contract or arrangement by which the Company, any Subsidiary or any of their assets or properties is bound or subject;

               (v) any transaction between the Company or any Subsidiary, on the one hand, and any of its officers or directors, on the other hand, that would be required to be disclosed pursuant to Item 404(a), (b) or (c) of Regulation S-K of the SEC;

               (vi) any change by the Company in its accounting principles, methods or practices or in the manner in which it keeps its accounting books and records, except any such change required by a change in GAAP or by the SEC; or

               (vii) any other event or condition, either individually or collectively, that has had, or would be reasonably likely to have, a Material Adverse Effect.

         (n)  Intellectual Property . The Company and its Subsidiaries own or possess sufficient rights to use all patents, patent rights, inventions, trade secrets, know-how, trademarks, service marks, trade names, licenses, copyrights or other information (collectively, “ Intellectual Property ”) which are used to conduct their businesses as currently conducted, except where the failure to own or possess such sufficient rights would not reasonably be expected to result, either individually or in the aggregate, in a Material Adverse Effect. Neither the Company nor any Subsidiary has received any written notice of, and has no actual knowledge of, any infringement of or conflict with asserted rights of others with respect to any Intellectual Property which, either individually or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would reasonably be expected to have a Material Adverse Effect, and to the Company’s and each of the Subsidiaries’ knowledge, none of the patent rights owned or licensed by the Company or the Subsidiaries are unenforceable or invalid.

         (o)  Registration Rights . Except as provided in Section 5 herein, effective upon the Closing, the Company is not currently subject to any agreement providing any person or entity any rights (including piggyback registration rights) to have any securities of the Company registered with the SEC or registered or qualified with any other governmental authority that have not previously been satisfied.

         (p)  Title to Property and Assets . The properties and assets of the Company and the Subsidiaries are owned by the Company or the Subsidiaries free and clear of all mortgages, deeds of trust, liens, charges, encumbrances and security interests, except for (i) statutory liens for the payment of current taxes that are not yet delinquent and (ii) liens, encumbrances and security interests that arise in the ordinary course of business and do not in any material respect affect the business of the Company and the Subsidiaries as currently conducted. With respect to the property and assets it leases, each of the Company and the Subsidiaries is in compliance with such leases in all material respects.

         (q)  Taxes . The Company and the Subsidiaries have filed or have valid extensions of the time to file all necessary federal, state, and foreign income and franchise tax returns due prior to the date hereof or have requested extensions thereof (except in any case in which the failure to so file would not reasonably be expected to have a Material Adverse Effect) and has paid or accrued all taxes due.

         (r)  Internal Accounting Controls . The Company and each of the Subsidiaries maintain a system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations, (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain asset accountability, (iii) access to assets is permitted only in accordance with management’s general or specific authorization, and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

         (s)  Market . The Company has not taken and will not take, directly or indirectly, any action designed to, or that might reasonably be expected to cause or result in, stabilization or manipulation of the price of the Common Stock of the Company to facilitate the sale or resale of the Purchased Securities.

         (t)  Investment Company . The Company is not an “investment company” within the meaning of such term under the Investment Company Act of 1940, as amended.

         (u)  Application of Anti-Takeover Provisions . There is no control share acquisition, business combination, poison pill or other similar anti-takeover provision under the Company’s Articles of Incorporation (or similar charter documents) that would become applicable to the Purchasers as a result of the issuance of the Company Shares and Warrant Shares.

         (v)  General Solicitation . Neither the Company nor any other Person (as defined below) authorized by the Company to act on its behalf has engaged in a general solicitation or general advertising (within the meaning of Regulation D) of investors with respect

to offers or sales of the Purchased Securities. For purposes of this Agreement, “ Person ” means an individual or corporation, trust, incorporated or unincorporated association, joint venture, limited liability company, joint stock company, government (or an agency or subdivision thereof) or other entity of any kind.

         (w)  Registration Statement Matters . The Company currently meets the eligibility requirements for use of a Form S-3 Registration Statement for the resale of the Registrable Shares (as defined below) by the Purchasers. Assuming the completion and timely delivery of the Registration Statement/Suitability Questionnaire, attached hereto as Appendix II (the “ Registration Statement Questionnaire ”), by each Purchaser to the Company, the Company is not aware of any facts or circumstances that would prohibit or delay the preparation and filing of a registration statement with respect to the Registrable Shares.

         (x)  No Integrated Offering . Neither the Company, nor any Affiliate (as hereafter defined) of the Company, nor any person acting on its behalf has, directly or indirectly, made any offers or sales of any security or solicited any offers to buy any security, under circumstances that would cause this offering of the Purchased Securities to be integrated with prior offerings by the Company for purposes of the Securities Act, any applicable state securities laws or any applicable stockholder approval provisions, nor will the Company take any action or steps that would cause the offering of the Purchased Securities to be integrated with other offerings.

         For purposes of this Agreement, an “ Affiliate ” of any specified Person means any other Person directly or indirectly controlling, controlled by or under direct or indirect common control with such specified Person. For purposes of this definition, “ control ” means the power to direct the management and policies of such person or firm, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise.

         (y)  Trading and Registration Matters . The Common Stock of the Company is eligible for trading on The NASDAQ National Market under the ticker symbol “ZIXI”. The Company has taken no action designed to terminate, or likely to have the effect of terminating, the listing of the Common Stock on the NASDAQ National Market.

      4.  REPRESENTATIONS, WARRANTIES AND CERTAIN AGREEMENTS OF THE PURCHASERS . Each Purchaser, severally and not jointly, hereby represents and warrants to the Company, and agrees that:

         (a)  Organization . Such Purchaser has all corporate, limited liability company, partnership, trust or individual, as the case may be, power and authority required to enter into this Agreement and the other agreements, instruments and documents contemplated hereby, and to consummate the transactions contemplated hereby and thereby.

         (b)  Due Authorization . All corporate, limited liability company, partnership, trust or individual, as the case may be, action on the part of such Purchaser necessary for the authorization, execution, delivery of and the performance of all obligations of such Purchaser under this Agreement have been taken and no further consent or authorization of such Purchaser is necessary, and this Agreement constitutes such Purchaser’s legal, valid and binding obligation,

enforceable in accordance with its terms, except (i) as may be limited by (1) applicable bankruptcy, insolvency, reorganization or other laws of general application relating to or affecting the enforcement of creditors’ rights generally and (2) the effect of rules of law governing the availability of equitable remedies and (ii) as rights to indemnity or contribution may be limited under federal or state securities laws or by principles of public policy thereunder.

         (c)  Non-Contravention . The execution, delivery and performance of this Agreement by such Purchaser, and the consummation by such Purchaser of the transactions contemplated hereby, do not: (i) contravene or conflict with the organizational documents of such Purchaser; or (ii) constitute a violation of any provision of any federal, state, local or foreign law, rule, regulation, order or decree applicable to such Purchaser, except in the case of clause (ii), for such violations, breaches or defaults as would not be reasonably likely to have a material adverse effect on such Purchaser.

         (d)  Litigation . There is no Action pending to which such Purchaser is a party that is reasonably likely to prevent, enjoin, alter or delay the transactions contemplated by this Agreement.

         (e)  Purchase for Own Account . The Purchased Securities are being acquired for investment for such Purchaser’s own account, not as a nominee or agent, in the ordinary course of business, and not with a view to the public resale or distribution thereof within the meaning of the Securities Act. Such Purchaser also represents that it has not been formed for the specific purpose of acquiring the Purchased Securities. Such Purchaser does not have any agreement or understanding, direct or indirect, with any other Person to sell or otherwise distribute the Purchased Securities. Notwithstanding the foregoing, the parties hereto acknowledge such Purchaser’s right at all times to sell or otherwise dispose of all or any part of such securities in compliance with applicable federal and state securities laws and as otherwise contemplated by this Agreement.

         (f)  Investment Experience . Such Purchaser understands that the purchase of the Purchased Securities involves substantial risk. Such Purchaser has experience as an investor in securities of companies and acknowledges that it can bear the economic risk of its investment in the Purchased Securities and has such knowledge and experience in financial or business matters that it is capable of evaluating the merits and risks of this investment in the Purchased Securities and protecting its own interests in connection with this investment.

         (g)  Accredited Purchaser Status . Such Purchaser is an “accredited investor” within the meaning of Regulation D promulgated under the Securities Act.

         (h)  Reliance Upon Purchaser’s Representations . Such Purchaser understands that the sale of the Purchased Securities to it will not be registered under the Securities Act on the ground that such issuance and sale will be exempt from registration under the Securities Act, and that the Company’s reliance on such exemption is based on each Purchaser’s representations set forth herein.

         (i)  Receipt of Information . Such Purchaser has (i) had access to the Company’s SEC Documents and (ii) has had an opportunity to ask questions and receive answers

from the Company regarding the terms and conditions of the sale of the Purchased Securities and the business, properties, prospects and financial condition of the Company and to obtain any additional information requested and has received and considered all information it deems relevant to make an informed decision to purchase the Purchased Securities.

         (j)  Restricted Securities and Restrictions on Transfer .

               (i) Such Purchaser understands that the Purchased Securities and the Warrant Shares have not been registered under the Securities Act and will not sell, offer to sell, assign, pledge, hypothecate or otherwise transfer any of the Purchased Securities or the Warrant Shares (except as permitted in Section 4(k) below) unless (A) pursuant to an effective registration statement under the Securities Act, (B) such Purchaser provides a reasonably acceptable legal opinion to the Company, to the effect that a sale, assignment, pledge, hypothecation or other transfer of the Purchased Securities or the Warrant Shares, as the case may be, may be made without registration under the Securities Act and the transferee agrees to be bound by the terms and conditions of this Agreement, (C) such Purchaser provides the Company a “no action” letter from the SEC to the effect that the transfer of the Purchased Securities or the Warrant Shares, as the case may be, without registration will not result in a recommendation by the Staff of the SEC that enforcement action by taken with respect thereto, (D) such Purchaser provides the Company with reasonable assurances (in the form of seller and broker representation letters) that the Purchased Securities or the Warrant Shares, as the case may be, can be sold pursuant to Rule 144 promulgated under the Securities Act (“ Rule 144 ”), (E) such Purchaser provides the Company with reasonable assurances (in the form of seller representation letters) that the Purchased Securities or the Warrant Shares, as the case may be, can be sold pursuant to Rule 144(k) promulgated under the Securities Act following the applicable holding period or (F) pursuant to any other exception contained in the Securities Act provided that the Purchaser provides a reasonably acceptable legal opinion to the Company. Notwithstanding anything to the contrary contained in this Agreement, including but not limited to in Section 5(c)(i) below, such Purchaser may transfer the Purchased Securities or the Warrant Shares to its Affiliates provided that (X) such Purchas