The first version of SNI support for Mail is available in Plesk Obsidian: https://docs.plesk.com/release-notes/obsidian/change-log/#18-rc10
You need MailEnable 10.20+ (for Windows) or Postfix 3.4+ and Dovecot (for Linux) to test it.
There are cases when it doesn’t work (e.g., if you connect to mail.domain.com it will not work, please use domain.com in connection settings of your mail client) that’s why we don’t mark it as “available”. We plan to fix these issues soon.
— rkKrisperx commented
This functionality is absolutely important and higly needed.
Many customers are complaining regarding issues with mail ssl certificates problems.
This issue requires an urgent fix.
It's obvsiously good news that the team working on linux postfix is taking care of the problem - only hope is that this will be addressed very fast also by Plesk... Kind regards