Login error from Microsoft about Incorrect Username

While logging into EUM Portal, or a SharePoint site, as a user registered with EUM, Microsoft might display an error saying the username may be incorrect.

For logging in with Email

As the error message states, this might be a misspelled email address and Microsoft cannot recognize this. Please check the email used here for login, correct it, and continue to sign in.

For logging in with Mobile Number (SMS Authentication)

One might see an incorrect username message from Microsoft when trying to login with a registered mobile number that would normally receive an SMS with a One Time Passcode to login.

This could be because Microsoft blocks any user from logging in, whose email address has the root domain verified in Microsoft Entra (Azure AD).

In the below example, demo.com is a verified domain in Microsoft Entra (Azure AD), and any Guest User using a Subdomain of this would see the "username may be incorrect" error message from Microsoft while logging in.