Exchange Password Required Messages

On an iMac with 10.15.7 OS

I have 2 Microsoft Exchange email accounts. Although I have Outlook installed on my Mac, I rarely use it and access my email and calendar through the Mac Mail client. Lately, I receive annoying notifications several times per day on my Mac. The graphic is attached.

The email is working fine. It doesn't matter how many times I verify the password for these accounts, and this notification appears within minutes again. Yesterday I logged into the Online Microsoft site to change my passwords for both accounts, which may be something causing these notifications. I successfully changed the PWs, and they had zero impact.

I have also read an older thread on this topic here from 2020. I tried everything that was recommended. Nothing worked.

My iPhone and iPad have these email accounts initiated in the mail apps there as well. So I don't know if there's some race condition causing this.

Any help would be appreciated.

Peter