Outlook 2016 doesn't accept password or app password

. I was also experiencing the problem with Thunderbird and enabling Oath2 authorization fixed it ! There's no such option in Outlook for windows.

Outlook for Windows does support OAuth2. Remove and re-add the account but make sure you enter your main outlook.com password, not your app password.

I created the registry key you suggested, but still the problem persists. I am on Office 365 running Windows 11 with all the latest updates.

The username/password combo is not wrong, if you press OK a few times on the error box that appears, it will finally login, only to randomly fail again later.

The problem appeared sometime within the last 10-15 days, at first it was happening with the SMTP outlook server, the problem with the SMTP server resolved itself after a few days but now same problem happens with the IMAP outlook server.

I've been troubleshooting it for at least 12 hours, also spent 2 hours last night with Microsoft level-1 tech support through Quick Assist, they couldn't find a solution so they escalated it to L2 but I'm sure they won't be of any help either because I am almost sure it's a Microsoft problem. Something must have changed on the IMAP server and/or the end-user client (Windows PC) through windows updates (something that probably has to do with authorization), and the problem started appearing.

It was also a problem with Thunderbird, and it seems to have been fixed when the user enabled Oath2 authorization in Thunderbird. I was also experiencing the problem with Thunderbird and enabling Oath2 authorization fixed it ! There's no such option in Outlook for windows.

Just posting this in case MS techs need further info on troubleshooting the problem. Keep in mind that the Outlook app for android and the outlook webmail work without problems. I'll just stick to Thunderbird for the time being, until this is resolved.

I think it originated from same source as MS 365 outage and once they will figure out what was done to it, it will be resolved. I have same issue with Office Outlook 2013 on 3 different machines and probably on 4th too, but none with Windows Mail app. Which is horrible substitution for Outlook, but it works as well as webpage which now mostly fully functional. It went to point of some things not working in web Outlook as well. Issue is not on our end but on Miscrosoft's. 365 installation took it better, but exhibited some other glitches.

I have the same issue, a couple days ago everything stopped syncing with Office 365, my desktop Microsoft Outlook Client, as well as my phone Outlook Client (using 9Folders). Nothing can authenticate or contact the server to send/receive emails.

I also tried to reset the app on my phone, deleted all the data and setup again - with no solution, now everything is gone off my phone and I cannot setup to resync (contacts, emails, tasks, etc.)

Microsoft please HELP quickly as this is crippling!!!

I have the same issue from 3 days ago, synchronizing Outlook2016 to Outlook.com and Hotmail.com. Yahoo and iCloud continue to work fine. Steps tried:

1- Remove the requirement for App Password and go back to single identification: both accounts are connected but password requests intermittently (frequently enough but not at regular send/receive intervals).

2- Password cleared in Credential Manager: no change

3- Change the IMAP server to outlook.office365.com for both: no change

Both accounts work fine with the iPhone Mail