I'll answer myself: I tried to migrate a couple of small servers from the 8930 to the new 8972.
Result: some users (only 3-4, luckily there are 2 servers with a few dozen users in total) have started to report that they no longer receive emails on MS Outlook (MAPI), while on WebMail everything is OK.
Maybe it's a stupid thing that can be solved in 2 minutes, but unfortunately I don't have time to test and/or open tickets theese days, so... Let's go back to the old 8930...
Gabriele Maoret - Head of SysAdmins at SERSIS
Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)