Microsoft fixes Windows Classic Outlook CAA2000B and 4usqa sign-in errors

The issue plagued users for over a week

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by Rishaj Upadhyay 

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Classic Outlook users have been frustrated by several changes and bugs coming their way. Recently, Microsoft confirmed that it has fixed CPU spike bug. Well, there wasn’t just one bug tied to Classic Outlook. Starting May 7, 2025, usres with Classic Outlook on Windows reported error codes like 4usqa and CAA2000B.

The error messages read, “Something went wrong” and “We couldn’t sign you in. Contact your system administrator.” The CAA2000B error specifically mentioned, “AADSTS500014: The service principal for the resource is disabled.“

Sign-in issue error message 4usqa Windows Classic Outlook
Image: Microsoft
Sign-in issue error message CAA20008 Windows Classic Outlook
Image: Microsoft

On the other hand, Outlook for Mac users saw a related sign-in error called 49dvs. Microsoft mentions that initial support cases hinted at a disabled service principal linked to the Microsoft Information Protection API.

Sign-in issue error message Outlook for Mac

Microsoft has fixed sign-in issues which troubled Windows Classic Outlook users

Fast forward to May 14, 2025, Microsoft has fixed sign-in issues related to Windows Classic Outlook and Outlook for Mac. The company says that users need to restart Outlook to apply the fix.

Admins looking to wanting to prevent this from happening again, Microsoft suggests enabling sign-in for the Microsoft Information Protection API:

  • Log in to the Microsoft Entra portal.
  • Search for “Information Protection” or the ID: 40775b29-2688-46b6-a3b5-b256bd04df9f.
  • On the API page, set “Enabled for users to sign in” to Yes.
  • Save the changes.

The full incident details can be found on the Microsoft 365 Service Health Dashboard under incident EX1072812.

More about the topics: Outlook, Outlook Errors

Rishaj Upadhyay

Rishaj Upadhyay Shield

News Editor

Rishaj is a tech writer who has been writing professionally for over four years, with a passion for Android, Windows, and all things tech. He initially joined Windows Report as a tech journalist and is now taking over as a news editor. He also writes for AndroidHeadlines. In the past, he has covered features, guides, and listicles for YTECHB and TechieTechTech. When he's not breaking the keyboard, you can find him cooking, or listening to music/podcasts.

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