Your network contains an Active Directory forest named adatum.local. The forest contains 500 users and
uses adatum.com as a UPN suffix.
You deploy a Microsoft 365 tenant.
You implement directory synchronization and sync only 50 support users.
You discover that five of the synchronized users have usernames that use a UPN suffix of
onmicrosoft.com.
You need to ensure that all synchronized identities retain the UPN set in their on-premises user account.
What should you do?