I have somehow ended up with a personal and work account for the same email address.

Hi Tony Sitterly,

Thank you for your valuable information and for taking the time to troubleshoot this thoroughly.

Your personal Microsoft account changes have been applied at the account level; however, these updates do not automatically sync with the UserID or identity data stored within your client organizations’ tenants. As a result, their IT administrators will need to update your information manually on their side.

Given your current situation, there is unfortunately limited action that can be taken from the end-user side. I would recommend reaching out to the IT administrator of your client organizations to assist further with this issue.

They can review your guest account configuration and update your external display name (for example, changing it to the .email format) in the Microsoft 365 Admin Center>Active users > Users > Your accounts > Display name to ensure there is a clear distinction and avoid conflicts with your previous .com personal account.

This can help preserve the existing data associated with your account.

However, if the issue persists, the IT administrator may consider removing your guest account and re-adding it to reset the identity association and resolve the conflict. Please note that this step could result in some data loss if the data's associated with the old external accounts.

If needed, the IT administrator can also contact Microsoft Support through the Microsoft 365 Admin Center on your behalf to further investigate and assist with clearing any deeply cached identity data and updating your user identity within their tenant.

This route ensures that a Microsoft support engineer can initiate a remote session to investigate backend configurations, run advanced diagnostic tools, and, if necessary, escalate the case to specialized teams with access to internal systems and logs. These backend resources are essential for resolving issues that go beyond what’s visible in the user interface.

As community moderators, we’re here to guide you, but due to privacy and security limitations, we don’t have access to the backend tools required for a full resolution. For this reason, contacting Microsoft Support via the Admin Center is the most secure and efficient way forward.

I sincerely recommend your IT admin to create a support ticket from Microsoft 365 Admin Center > Support > Help & Support.  

Microsoft also provides customer service phone numbers based on your region. You can find the appropriate contact number here: Customer service phone numbers - Microsoft Support 

I hope this helps you resolve the issue quickly. I’m glad to assist and truly hope the information provided has been useful. Please feel free to reach out anytime if you need further assistance.  

If you find my post helpful, kindly consider marking it as the accepted answer. Doing so can assist others in the community who may have similar questions in finding solutions more quickly.  

Thank you for your kindness and contributions to the forum. 

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The behavior is caused by having both a personal Microsoft account (MSA) and a work/school account using the same email address. Even after renaming the personal account and removing the original alias, sign-in experiences can still be confused when both identities exist.

From the documented guidance, the supported ways to resolve this type of overlap are:

1. Rename or re-alias the personal Microsoft account so it no longer uses the work-style address
   • This has already been done: the personal account’s primary alias was changed from the .com address to a different domain (for example, .email), and the .com alias was removed.
   • This is the recommended step to create a clear separation between personal and work identities.
   • The official guidance for this scenario is to go to the Manage how you sign in section of the Microsoft account and change or add aliases, then set the correct one as primary. For reference, see the “How can I get rid of the prompt?” section in the “Which account do you want to use?” article.
2. Understand that the same email cannot be used as a new personal account if the domain is in Microsoft Entra ID
   • When a domain is hosted in Microsoft Entra ID (for example, because it is used with Microsoft 365 or another Azure-based service), new personal Microsoft accounts cannot be created with that domain. This is to avoid exactly this overlap between personal and work accounts.
   • Existing overlapping accounts are not automatically removed; they must be separated by renaming the personal account, as already done.
3. When Teams sign-in is blocked by overlapping accounts
   • The documented Teams guidance for overlapping work/personal identities is:
     • Use a private/incognito browser and go to https://teams.microsoft.com.
     • Sign in explicitly with the work or school account.
     • If that fails because the email is tied to both a work and a personal account, the resolution is to unlink the two accounts by changing the email address or phone number for the Microsoft account (personal) so that the work address is no longer used as an MSA.
   • This aligns with the steps already taken: changing the personal account alias and removing the .com alias.
4. When the overlap persists after alias changes
   • The documentation does not provide additional self-service steps beyond:
     • Renaming/removing the overlapping personal alias.
     • Using private/incognito sessions and explicitly choosing the work account.
   • For persistent issues where the client continues to pick the wrong identity even after the alias has been removed and caches/credentials cleared, the remaining path is to work with Microsoft support so they can address the identity overlap on the backend.

Given the steps already completed (alias change, removal of the .com alias from the personal account, cache and credential cleanup, Teams reinstall) match the documented remediation, and the problem persists, the next step is to contact Microsoft support and have them correct or remove the stale personal identity that is still associated with the .com address so that Teams sign-in resolves to the work account only.

References:

• Which account do you want to use?
• "Someone has already set up Teams for your organization" error in Microsoft Teams
• Troubleshooting suggestions for signing in to Visual Studio subscriptions
• Services Hub sign in FAQs