The client is experiencing migration failures for emails with sensitivity labels and wants to know whether re-migrating the mailbox without labels will migrate all 50K emails or only the 3K items that previously failed.
The migration failures occur because the affected emails are protected with sensitivity labels that were created and managed by a different organization (3rd Party Sensitivity Label). These labels enforce encryption and access restrictions that prevent the migration tool from reading or processing the messages, resulting in failed items during migration.
Emails that were successfully migrated during the initial migration will not be migrated again during a delta sync unless changes were made to those emails. When running a delta sync with sensitivity labels unchecked, only the emails that previously failed or were not migrated will be migrated to the target; successfully migrated emails will not be re-migrated.
