Exhibit 10.28

AMENDMENT NO. 1

TO ZIX CORPORATION STOCK OPTION AGREEMENT

This Amendment No. 1 (this “Amendment”) is entered into as of January 18, 2016,
between Richard Spurr (the “Optionee”) and Zix Corporation, a Texas corporation
(the “Company”).  Reference is made to that certain Zix Corporation Stock Option
Agreement, dated as of January 9, 2008, between the Optionee and the Company
(the “Option Agreement”).

1. Amendment.  

(a) The first sentence of Section 4 of the Option Agreement is hereby deleted
and replaced with the following:

“In the event the Optionee ceases to be an employee of either the Company or a
Subsidiary of the Company due to death, Retirement, Resignation, Disability or
termination by the Company for any reason other than “cause” (such five events
each being a “Qualified Termination”), this Option may be exercised by the
Optionee or his or her estate, personal representative or beneficiary with
respect to all options that are vested as of the day of such employment
termination (including without limitation, those that vest pursuant to the
second sentence of subparagraph 3.a), until the later of (i) at any time within
the one-year period commencing on the day next following such employment
termination in the case of any Qualified Termination and (ii) at any time until
the first anniversary of the date that the Optionee ceases to be a member of the
Board (or in any such case in (i) or (ii) above, if shorter, only for the
remaining stated term of this Option).”

(b) The following sentence is hereby inserted at the end of the first paragraph
in Section 4 of the Option Agreement:

“If the Optionee’s directorship is terminated by a vote of the shareholders or
directors for “cause”, this Option shall automatically expire simultaneously
with such termination.”

2. Governing Law. This Amendment is governed by and will be construed,
interpreted and enforced in accordance with, the laws of the State of Texas
(excluding its conflict of law rules) and applicable federal law.

3. Counterparts. This Amendment may be executed in any number of counterparts,
all of which shall constitute one and the same agreement, and any party hereto
may execute this Amendment by signing and delivering one or more counterparts.
Delivery of an executed counterpart of this Amendment electronically or by
facsimile shall be effective as delivery of an original executed counterpart of
this Amendment.

 

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4. No Other Changes. Other than as provided in this Amendment, the Option
Agreement is and shall remain in full force and effect.

[SIGNATURE PAGE FOLLOWS]

 

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IN WITNESS WHEREOF, the parties hereto have executed this Amendment on the dates
set forth below, to be effective as of the latest date set forth below.

 

ZIX CORPORATION

 

 

 

By:

 

/s/ Justin Ferguson

 

 

Justin Ferguson,

 

 

Vice President and General Counsel

 

 

 

Date:

 

January 18, 2016

 

/s/ Richard Spurr

Richard Spurr

 

 

 

Date:

 

1/18/2016