Please note that in the MFA platform all identities are converted to lowercase. Hence, if you assign an email containing uppercase characters to a Windows user in Active Directory the user will be required to authenticate with the lowercase equivalent. For example John.Smith@example.com will need to authenticate as firstname.lastname@example.org.
For each user, the 'user logon name' in their 'Account' tab is their AD username which they will use in the Primary Authentication phase of the login process:
The email address entered in the 'General' tab is then the email that they must use for the MFA stage of the authentication process - i.e. with the MIRACL authentication server: