sygnus21 said:
I ask because I've been a long time Norton user (the last being Norton 365 under Win 7) and never had an issue with IMAP accounts using the Outlook desktop app. On the flipside I rarely use plugins for Outlook (currently just Acrobat enabled on 365 desktop app). My only AV installed is Defender.

That issue just sounds odd but ok.
I think the issue presents its self when all accounts are POP Secure SSL and or IMAP, these account Norton anti Spam can not see into therefor the password issue pop up occurs. As soon as the AntiSpam plug in is disabled the issue goes away. Still don't know that this is the OPs issue