In AAD Connect it’s possible to sync only users with specific UserPrincipalName. And here is how to do it.
- Open Synchronization Rules Editor
- Under Rule Types click on Outbound.
- Find the rule named Out to AAD – User Join. Click Edit.
- Click Scoping filter on the left hand navigation. Click Add clause and in Attribute select userPrincipalName, in Operator select ENDSWITH, and in Value type @contoso.com.
- Click Save.
- Perform a full sync: on the Connectors tab, right-click SourceAD, click Run, click Full Synchronization, and then click OK.
- Start normal sync or wait for the time period you have specified.