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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - Q ( Mark One ) ☑ ☐ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30 , 2021 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number : 0-17995 zix ZIX CORPORATION ( Exact Name of Registrant as Specified in its Charter ) Texas ( State of Incorporation ) 75-2216818 ( I.R.S. Employer Identification Number ) 2711 North Haskell Avenue Suite 2300 , LB 36 Dallas , Texas 75204-2960 ( Address of Principal Executive Offices ) ( 214 ) 370-2000 ( Registrant's Telephone Number , Including Area Code ) Indicate by check mark whether the Registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the Registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes ☑ No □ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes ☑ No ☐ Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , ” “ smaller reporting company , " and " emerging growth company ” in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer Emerging growth company ☐ ☐ Accelerated filer Smaller reporting company If an emerging growth company , indicated by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes ☐ Indicate the number of shares outstanding of each of the issuer's classes of common stock , as of the latest practicable date . Class Common Stock , par value $ 0.01 per share Securities registered pursuant to Section 12 ( b ) of the Exchange Act : Title of Each Class Common Stock , par value $ 0.01 per share Trading Symbols ( s ) ZIXI Outstanding at November 5 , 2021 56,790,468 No ☑ ☐ ☑ ☐ Name of Exchange on Which Registered NASDAQ Global Market