access to accounts

The old work account cannot be deleted from the personal Microsoft account side, and the two accounts cannot be merged.

What can be done:

1. Rename the personal Microsoft account so it no longer uses the same email address.
   • Go to the Manage how you sign in section of the Microsoft account.
   • Set a different existing address as primary, or add a new alias and make it primary.
   • This removes the sign-in conflict that causes the “Which account do you want to use?” prompt.
2. Ask the organization that owns the old work account to remove or disable that work or school account.
   • Work or school accounts are created and managed by an organization administrator.
   • If the old work account still exists, only that organization can remove it on their side.
3. Remove the old account from Outlook on Windows if it is still added there.
   • In new Outlook: View tab > View settings > Accounts > Your accounts.
   • Find the old account, select Manage, then Remove.
   • This removes the account from Outlook only; it does not delete the account itself.
   • Any offline cached content for that account will be deleted when it is removed.
4. If Outlook is sending or mapping mail to the wrong account because multiple accounts are in the same profile, remove and then re-add the secondary account.
   • Open Control Panel > search for mail > Mail > E-mail Accounts.
   • Select the secondary account and choose Remove.
   • Close Outlook.
   • Go back to Mail > E-mail Accounts > New and add the account again.
   • Send a test message to confirm the account is now set up correctly.
5. If Outlook setup fails because the same email address is also used by another provider account, an Exchange admin can create a new Microsoft 365 alias and use that alias during Outlook setup.

The uppercase/lowercase difference in the address does not change the fact that both accounts are using the same email address. The supported fix is to separate the sign-in identities by changing the personal account alias, and have the old organization remove the work account if it is no longer needed.

• Which account do you want to use? | Microsoft Support
• Add an email account to Outlook for Windows | Microsoft Support
• New Outlook
• Email messages are sent to the wrong account when multiple accounts are associated with an Outlook profile
• Connection to Microsoft Exchange is unavailable error when a Microsoft 365 user tries to set up Outlook
• What's the difference between a Microsoft account and a work or school account? | Microsoft Support