MFA & Verification Issues

Fix Microsoft Authenticator Requesting MFA for Old Alias Account

Maira Mehtab Sep 20, 2026 868 views

Question details

Users are being prompted by Microsoft Authenticator to provide MFA for an older, unregistered email alias when trying to access a SharePoint site hosted in an external tenant.

Product: Microsoft Authenticator / SharePoint
Device & OS: not provided
Scenario: Accessing a SharePoint site in an external tenant using a current email account, but the system mistakenly prompts for MFA on an outdated alias.
Observed behavior: The authentication fails or stalls because the requested MFA verification targets an old @domain2.com alias that is not set up or registered in the user's Microsoft Authenticator app.

Before you start

Ensure you have the contact information for the IT administrator of the external SharePoint tenant, as this issue requires administrative access in the host directory to resolve.

Solution 1Recommended

Contact the External SharePoint Administrator

The most effective way to resolve alias mismatches is by having the external tenant administrator update your guest account configuration in their directory.

Because the SharePoint site is hosted in another organization's tenant, their Microsoft Entra ID (Azure AD) still holds your outdated alias as your primary guest identity. You cannot change this from your own account settings.

Identify the external admin

Contact the IT support desk or the administrator of the organization that is hosting the SharePoint tenant you are trying to access.

Request a guest account review

Ask the administrator to locate your guest account properties within their Microsoft Entra ID portal.

Update the sign-in identity

Request that they remove the outdated alias and ensure your primary current account is set as the correct sign-in identity.

Reset MFA methods

Have the administrator select the 'Require re-register MFA' option for your guest profile. This will allow you to set up Microsoft Authenticator freshly with your current account upon your next login.

Admin action required: Only an administrator with appropriate directory permissions in the external tenant can perform these resets.

Solution 2

Seek Specialized Assistance from Microsoft Forums

If administrative resets do not completely resolve the issue, consult the official Microsoft Authenticator community for specialized troubleshooting.

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Frequently Asked Questions

Why does SharePoint ask for MFA on my old email alias?

When you were originally added as a guest to the external tenant, your old alias was recorded. The external tenant's directory still retains this outdated identity for your guest account, even if you updated it on your own end.

Can I fix the old alias MFA issue directly from my Authenticator app?

No. The authentication requirement is being strictly enforced by the external organization's directory policies. Their administrator must update your profile or reset your MFA status on their side.

How do I re-register my MFA for a SharePoint guest account?

Once the external administrator selects 'Require re-register MFA' for your guest profile in their admin center, you will automatically be prompted to set up Microsoft Authenticator again the next time you log into their SharePoint site.

Login & Account Issues