You need to resolve the Active Directory issue.
What should you do?
A . From Active Directory Users and Computers, select the user accounts, and then modify the User Principal Name value.
B . Run idfix.exe, and then use the Edit action.
C . From Active Directory Domains and Trusts, modify the list of UPN suffixes.
D . From Azure AD Connect, modify the outbound synchronization rule.
IdFix is used to perform discovery and remediation of identity objects and their attributes in an on-premises Active Directory environment in preparation for migration to Azure Active Directory. IdFix is intended for the Active Directory administrators responsible for directory synchronization with Azure Active Directory.
Scenario: Active Directory Issue Several users in humongousinsurance.com have UPNs that contain special characters. You suspect that some of the characters are unsupported in Azure AD.