Outlook 2016 doesn't accept password or app password

OAuth2 works fine, but is not an option in some clients.

This link in the article is interesting: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basic-authentication-exchange-online 

It confirms OAuth2 has been mandatory for business users for over a year.

It is very likely then that this requirement has been accidentally leaked on to consumer accounts for a large percentage of connection attempts.

Unfortunately, it seems most email clients don't support exchange accounts for personal Microsoft accounts.(paid or free doesn't matter.) I know Mailbird doesn't, at least in version 2.

Those that do, that might work. It would explain why my phone and tablet, both of which support my Microsoft account as an exchange account, have had zero issues with my outllok email account on either.

I just tested it with my hotmail and Thunderbird and it worked for me.

I also had to change IMAP server to outlook.office365.com

My app password hasn't been rejected for over an hour, looks like Microsoft have finally resolved it

I have made no changes to any server settings from before this all started Jan. 23, and I have been running several tests on older clients and systems including Windows Live Mail using IMAP configured to imap-mail.outlook.com with SSL/TLS using app passwords with normal authentication method (not OAuth2, etc.) as well as Thunderbird.

Where before, since Jan. 23, clients were experiencing intermittent yet consistent errors authenticating account logins, for the first time since Jan. 23, I am now having no issues at all syncing all accounts including *Hotmail.com, *Live.com, and *Live.ca, as we had no issues with these same configurations prior to Jan. 23.

Unless it is just a coincidence, it seems functionality has been restored for us.