Outlook email keeps prompting for a password, and then not accept it. Blocked out of emails.

Some reason (I suppose from an older Microsoft article) the registry key HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity - EnableADAL was set to 0. This key hadn't been changed manually before Outlook started choking. Maybe Outlook 365 was enabling modern authentication by default (which makes sense), and ignoring the key. Why it started paying attention to the key, I don't know.

I set it to value = 1 and Outlook logged in immediately.

This problem started for me on 2-28-2025. I am using the latest updated version of Office 365 and Outlook opens but immediately prompts with a Windows Security window, Microsoft Outlook , Connecting to .... , User name text field, Password text field, Remember my credentials check box, OK and Cancel buttons.

Password entered correctly and click OK, and I can do this as many times as I want, over and over, and never get anywhere.

I have uninstalled Office completely and used Revo uninstaller to search for leftovers.

I deleted the Outlook profile after uninstallation.

I deleted every single saved credential in Credential Manager.

I removed the Microsoft Account in Settings on Windows 11.

I removed the saved Profile in Microsoft Edge and fully cleared the cache.

Reinstalled from the link inside my Office 365 account through Microsoft Edge. Created a new Outlook profile and was able to use Outlook for 1 day. Upon launch the next day, the same prompt appears.

This reminds me of something Microsoft SARA was able to fix, but that is discontinued now and the "Get Help" app only leads to web searches. When I was able to try starting a troubleshooting guide, it errored out with "Protocol not enabled". No clue what that means.

Subscription is Microsoft 365 Business Premium.

Outlook profile is linked to the Exchange account in the Business Premium account. That is the only email account in the Outlook profile.

Outlook is bricked. I really don't want to work with the web version. That just isn't a possibility. How can this be fixed?

I can bypass the password prompt by clicking "Cancel," which allows me to access Outlook, but this is not a sustainable solution. Since then, I’ve been using the new Outlook or Outlook on the web without any problems, but they don’t fully meet my needs like Classic Outlook does.

Here are the answers to your queries:

Mailbox extension: .pst

Type of Account: Company/school use (Microsoft 365 account)

Software Version: Microsoft 365, fully updated (Version 2501 Build 16.0.18429.20044). I also ran an Office Online Repair today.

Protocol: IMAP

Additionally, I have already tried the following steps without success:

Cleared cached credentials in the Windows Credential Manager.

Verified Modern Authentication is enabled and configured properly.

Reset network settings.

Used the Support and Recovery Assistant (SaRA) tool for troubleshooting.

Ran Outlook in Safe Mode and attempted to disable add-ins.

Repaired Outlook data files with SCANPST.

The issue persists even with these efforts. Any suggestions or further steps I can try would be greatly appreciated.

PS.: I tried to inset a screenshot without success

Hello, here is what I have:

1. Comcast, via Outlook
2. Personal
3. Microsoft 365, updated
4. IMAP

Thanks for looking into this. I noticed the glitch started about the same time I opened the new MS Pilot. Coincidence?

(Note, I cannot send a screenshot of the popup because now the Office email app will not even open when I click on it. This was after entering the password several time yesterday which it never did accept (have checked and confirmed the password). I am really locked out. It opened briefly last nite and loaded some emails, now its gone dark again. On a second computer it never did load any emails).

Dear DRL5606

Welcome to Microsoft Community.

According to the content of your description, you have been prompting the problem of wrong password when using Outlook, right?

I would like to confirm something about your problem:

1. What is the mailbox extension you are using? (Outlook/Hotmail, Gamil, Yahoo)
2. Is your mailbox for company/school use or personal use?
3. What is the version of Office associated with Outlook that you are using? (Office2021, 2019, etc.)

4.What is the method by which your mailbox is configured? (POP/IMAP, etc.)

Since you have provided so little information, in order to be able to help you solve your problem, please let me know what you are inquiring about above as well as a screenshot of the problem you are having so that I can get an accurate picture of your problem.

Feel free to text back if you need further help.

Best wishes

Chris.S-MSFT | Microsoft Community Support Specialist