X0306 4 2021-03-01 0 0000855612 ZIX CORP ZIXI 0001488288 Miller Maribess L 2711 N. HASKELL AVENUE SUITE 2300 DALLAS TX 75204 1 0 0 0 Deferred Stock Units 2021-03-01 4 A 0 18059 0.00 A 113043 D Grant under the 2018 Omnibus Incentive Plan (the "Plan"). The deferred stock units will vest pro-rata and quarterly over one year, and subject to acceleration under conditions described in the Plan. Delivery of the underlying shares in respect of vesting will occur pursuant to the underlying award agreement. /s/ Noah F. Webster, Attorney-in-Fact 2021-03-03