I completely forgot to mention that I was/am using M365-IMAP with offlineimap to access the MS servers. However the problem seems to have been transient and has not recurred, so I intend to close this bug in the near future.
- Bug#1039008: offlineimap3: User is authenticated but not connected ael
- Bug#1039008: Perhaps resolved ael
- Bug#1039008: M365-IMAP ael
