Classic Outlook hit with more bugs Microsoft confirms CAA2000B, 4usqa, 49dvs sign-in issues

Microsoft recently addressed a major bug related to Classic Outlook and Word wherein typing would lead to high CPU usage with spikes of up to 50%.

Another Outlook bug has hit this time again on the classic app. Microsoft has confirmed sign-in troubles with error codes "CAA2000B, 4usqa, and 49dvs." This is the third major bug in the last month to affect Classic Outlook while Microsoft tries hard to transition away from it to New Outlook for Windows. Last month, downloads for Classic Outlook were affected.

About the new sign-in issue that affects both Outlook for Windows and Outlook for Mac, Microsoft writes:

Starting around May 7, 2025, some users that open classic Outlook get sign in errors like the following:

Error

Something when wrong. [4usqa]

Something went wrong

We couldn’t sign you in. If this error persists, contact your system administrator and provide the error code CAA2000B.

AADSTS500014: The service principal for the resource is disabled.

Some users that open Outlook for Mac get sign in errors like the following:

Error

Something when wrong. [49dvs]

Microsoft has learned that a disabled service principal "40775b29-2688-46b6-a3b5-b256bd04df9f" is causing the issue and thus re-enabling it is a way to fix these troubles.

The company has provided a detailed workaround for it. The tech giant writes:

The Outlook and Microsoft Information Protection Teams are investigating this issue. We will update this topic when we know more. This issue is also reported in the M365 Service Health Dashboard as EX1072812.

To mitigate the issue, enable users to sign-in for the Microsoft Information Protection API, by doing the following:

1. Sign in to the Entra portal, Microsoft Entra.

2. Search for Information Protection or 40775b29-2688-46b6-a3b5-b256bd04df9f and in the search results, select Microsoft Information Protection API.

3. On the Microsoft Information Protection API page, set Enabled for users to sign-in to Yes.

4. Select Save to apply the changes.

You can find the issue in this support article here on Microsoft's official website.