Limit which Microsoft account aliases can sign in

A personal Microsoft account can have several email or phone aliases that share one password, storage and subscriptions. By default, each may be usable to sign in. If an old public address attracts repeated login attempts, you can block that alias as a sign-in name without deleting the account or its mail.

Before you start​

This is for a personal Microsoft account, not a work or school tenant. Make sure at least one sign-in alias is current, known to you and supported by your password manager before editing preferences.

Do it step by step​

1. Go directly to account.microsoft.com in a trusted browser and open Your info → Sign-in preferences. Avoid a link from a security-warning email.
2. Review the full alias list and identify the address you use for sign-in versus addresses that only need to receive mail. Note which is primary before changing anything.
3. Choose which aliases are allowed to sign in. Disable sign-in for an exposed alias only after confirming another alias remains enabled; save the selection.
4. Open a private browser window and test sign-in with the allowed alias, completing the normal verification prompts. Do not sign out of your only working session until that test succeeds.
5. Check Outlook mail and subscriptions to confirm they still function. Update your password manager's username entry and tell no one the new alias merely for the sake of secrecy.

Check the result​

The permitted alias should work for sign-in, and your existing account data should still be present. A blocked alias may still receive email; test delivery separately if that matters.

If something goes wrong​

If you see 'username turned off,' try the allowed alias instead of resetting the password. If you disabled the wrong one while still signed in, return to Sign-in preferences and correct it.

Know the limit​

Alias controls do not replace a unique password and MFA. Microsoft says aliases share account settings and password, and that sign-in can be restricted per alias. Microsoft's alias sign-in controls