Hey there,
Yeah, ours still isn't playing ball. I've found out since that we pay for FMS support from the local council, i've been in touch with them and the lady I got freely admitted she wasn't technical enough to really be able to help but would get back to me, and to be fair she has. Important bit copied below:
"I logged a call with ESS and they have got back to me today.
They are aware of an issue with sending emails from FMS, where Office365 (Microsoft365) is the mailserver provider being used by the school to send emails.
They believe this to be related to a change made by Microsoft, investigation is still ongoing.
However, they have had a setting within O365 suggested as a possible fix for the email issue:
In the properties for the mail box user can you please go to Mail > Manage email apps and check the option "Turn on use of legacy TLS clients" "
I'd already tried what she suggested at the end earlier in week and it hadn't worked, but worth a pop, may work for you! :-)