Hello community, how are you?, I hope everybody is fine.
Here in Argentina and Chile have detected several clients that after migrating them to version 18.2.1 report problems sending emails to O365 domains.
The error reported in the GWIA logs is 550 Host Unknown.
After testing we have been able to detect that the GWIA uses TLS 1.0 regardless of the --sslOption that we use.
If we make the GWIA relay via an AntiSpam, the emails arrive correctly at their destination, since the AntiSpam (MailCleaner, SMG, etc) has no problem using the new versions of TLS.
Note: The minimum version accepted by O365 is 1.2.
In the meantime, I just opened a SR.