Error when opening SMTP Stream

Tony Burtovoy - 05:26pm, Oct 28 2020

Latest MDConnector(6.5.3), Latest MDx64(20.0.3).. although issue did occur on previous (20.0.2) as well.  Server is Win 2016 Std x64.. plenty of RAM, plenty of disk.. 100% up to date on MS updates since about 2 weeks ago.  Random Outlook users are getting this sort of error when sending mail: 

  "Error when opening SMTP stream" 

  "TLS/SSL failure for MAIL.DOMAIN.COM: Unexpected TCP input disconnect" 

Happens about once per week among all users.  There are there (90 employees about 25 Outlook 2013 users).  When the user gets the undeliverable but then tries again, it typically works just fine.  Seems to be only Outlook and very random, but not webmail. 

Here's what I seem to see in the server logfile (smtp-in) when this occurs: 

Mon 2020-10-19 11:00:34.962: Accepting SMTP connection from 10.0.0.148:56569 to 172.24.16.115:465 

Mon 2020-10-19 11:00:35.045: * SSL error 0x80090330 The specified data could not be decrypted. 

Mon 2020-10-19 11:00:35.045: SMTP session terminated (Bytes in/out: 508/3730) 

See attachment. Any ideas? 

-TonyAttachments: 
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