The Domain Rewrite license had expired, and after its renewal, user mailboxes were unexpectedly removed from their distribution groups.
OptInSync, our backend service, may take several hours to complete tasks like creating connectors, rules, groups, and syncing group membership. Once group membership is synced, additional time may be needed for Exchange to replicate the membership and start routing mail through those connectors for rewriting.
When Directory Replication (DR) for the project, is disabled/enabled it’s recommended to allow a few hours for a full synchronization. After that, if the accounts are still not appearing in the Distribution Lists within 2-3 hours, it's worth disabling and re-enabling DR for those specific accounts. This should ensure they are added to the correct Distribution Groups.
