My Hotmail account is being routed to Azure AD instead of the Microsoft Account (MSA) system.

Question

I need the identity routing reset.

Outlook Classic forces a work/school login and the login flow returns AADSTS900144.

This is a cloud‑side identity routing issue, not a device issue.

Answer 1

Dear @Craig Kaminski,

Thank you for posting your question in the Microsoft Q&A forum.

Before giving you the best solution, could you please confirm these questions below to help me diagnose the issue more effectively: 

• Do you recognize this tenant name, or do you recall ever being added as a guest user to this organization (for example, accepting an invitation to access another company’s Microsoft 365 or similar service using your Hotmail address)?
• Does the issue occur on all devices and browsers, including private/incognito mode?

The error message AADSTS900144 indicates that the request body is missing the login_hint parameter, which is required for Azure Active Directory (AAD) to identify the user account during authentication, especially when dealing with guest accounts.

In the meantime, here are some steps I recommend you try:

Step 1: Clear Outlook Classic Cache

• Close the Outlook app > Press the Windows + R keys simultaneously to open the Run dialog box. 
• Type the following path into the Run box and press Enter: %localappdata%\Microsoft\Outlook\RoamCache 
• This will open the RoamCache folder containing the cache files associated with your Outlook profile. Usually, it's located at: C:\Users{User name}\AppData\Local\Microsoft\Outlook\RoamCache 
• Click anywhere within the folder, press Ctrl + A to select all files, and then press the Delete key to remove them. Alternatively, you can right-click the selection and choose the Delete option from the context menu. 
• After clearing the cache, restart Outlook again. It will rebuild the necessary cache files from scratch. 
• For more detail, please refer to: How to clear Outlook cache in new app and classic version.

Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.

Step 2: Uninstall and reinstall classic Outlook on a Windows PC

For more information, please refer to Install or reinstall classic Outlook on a Windows PC

Step 3: Repair Outlook Profile

Follow these steps to let Outlook diagnose and fix errors in your Outlook mail profile that might be causing the issue. Visit: Fix your Outlook email connection by repairing your profile

Recommended Workaround:

While this is being investigated, I recommend you continue to access your email using Outlook on the web by signing in with your Hotmail email address.

Note: Please understand that as a forum moderator, my role is to provide general guidance and troubleshooting support. I don’t have access to internal systems or backend tools, and I appreciate your understanding of these limits.

I hope the information shared helps point you in the right direction. If you have any questions or need further clarification, please feel free to reach out.

The first response may not always resolve the issue right away, but with your help and more details, we can work toward a solution.

Thank you for your patience and understanding. I'm looking forward for your reply.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.