Using classic Outlook for Windows in business environments
The only two ways I've been able to get email through this episode are:
- With existing (and soon to be retired) IMAP settings (either server values), after each change of network state of the computer I slam the server with 10-20 or more consecutive send-receives across multiple email accounts, occasionally canceling all of those send-receives and repeating the process, and sometimes using a custom shortcut which runs a command to kill Outlook abruptly, then I restart Outlook and repeating the massive send and receive. Usually after a couple of minutes of that the IMAP counts connect and stay connected until the next time the network state is changed.
- re configuring all email accounts for modern authentication by doing so from within Outlook 2021 professional (freestanding) and allowing Outlook to auto configure as exchange (which is different here than the exchange option is when run from the Windows Control Panel email applet).
I'm actually writing up some new details to add to an exiting thread here: https://answers.microsoft.com/en-us/outlook_com/forum/outlk_win-outtop_classic-outsub_ofh/authentication-failure-repeated-request-for/bc06f09c-e695-4655-b90b-481fd926db4f
There are Notes from my earlier testing at the link above. Since then I was able to configure properly working new email accounts (but not IMAP) in Microsoft Outlook 2021 Professional by doing the configuration from within Outlook and letting Outlook auto-detect the settings. NOTE: the auto-detect may behave differently from the Control Panel applet and use IMAP instead of modern exchange, and accounts configured via the exchange option in the Control Panel applet behaves as IMAP does rather than as the auto configured exchange from within Outlook.
Also, there are problems with Microsoft servers which have affected even their webmail interface and email accounts configured for modern authentication but those are are less frequent transient errors than the issues reported in this and similar threads. Although these authentication issues are less serious they do complicate the testing of the more serious issues. this might also be the source of this recent episode of IMAP issues.
Additionally, I think that whatever services or resources Microsoft uses to process IMAP while people switch to modern authentication seem to be failing or limited.
Adding to this mess is the fact that Microsoft's documentation regarding proper configuration for modern authentication falls short and the new method of configuring accounts which they expect defies best practices for workstation building.
More testing observations in the linked post above within a couple of days.