Yahoo Email Sign In Prompt Repeatedly Pops Up In Outlook 365 Email

For Yahoo in classic Outlook, this is a known issue that caused repeated sign-in problems and sync failures. It was fixed in the Microsoft 365 service on 3/20/26, but after a Yahoo password change the old OAuth token can remain for about one hour. When that token expires, Outlook should prompt for sign-in again.

If the sign-in prompt keeps repeating, force Outlook to refresh the Yahoo credentials:

1. Close Outlook.
2. Open Credential Manager from the Windows Start menu. On Windows 10, this may be under Control Panel.
3. Select Windows Credentials.
4. Under Generic credentials, find entries that start with MicrosoftOffice16_Data:OAUTH2.
5. Expand them and identify the ones that include tp_yahoo_imap_Oauth2.
6. Select Remove for each Yahoo-related MicrosoftOffice16_Data:OAUTH2 entry. There can be two or four entries for the account.
7. Restart Outlook and sign in to the Yahoo account.
8. If mail does not start syncing immediately, restart Outlook once more.

If Outlook never asks for the Yahoo password during setup or re-setup, make sure Require logon using Secure Password Authentication (SPA) is unchecked.

If the credential removal does not fix it, there is a second workaround: delete the Yahoo identity key under:

Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities

Then restart Outlook and sign in again. This is a registry change, so use caution and only remove the identity key that matches the Yahoo account.

If needed, the Yahoo account can also be removed and added again in classic Outlook:

File > Account Settings > Account Settings > select the Yahoo account > Remove

Then add it again:

File > + Add Account > enter the Yahoo account > Connect > complete the Yahoo sign-in and permission prompts.

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