We're still occasionally hitting this exact issue with 1.18.0 - I see there's a 1.18.1 but the release notes don't indicate any changes to this side of things.
What I really want to know is - a reliable way to let us know when this has happened. Usually, the first indication is when someone says "Hey, it's been a bit quiet lately..."
This seems to fail silently, apart from when you go into the email settings. The admin webui interface doesn't show any mail failure logs, and the database table ost_syslog just gives lots of cron entries without any indication that the mail fetch failed. (Edit: It is possible the issue is on 365's side when we make a priv change)
Anyone know how I can alert my team when this has happened, so we can go through the re-auth process again?