Configure this policy setting to force all users that require MFA to log in to the machine using the UPN format of: email@example.com. There are two settings for this group policy:
If this policy is set to Enabled, all users that require MFA must log in using the UPN format, otherwise an error message appears "Invalid User. Please use format firstname.lastname@example.org and try again."
Note: All users that do not require MFA can log in using either the UPN format or NT account format.
- If this policy is set to Disabled or Not Configured, all users can log in using either the UPN format or NT account format.