Target mailbox unlock operation was not replicated message after migrating a mailbox
Original KB number: 3078572
Symptoms
After you move a mailbox from the on-premises Microsoft Exchange Server environment to Microsoft Exchange Online in Microsoft 365 in a hybrid deployment, you receive the following warning message:
Warning: Target mailbox unlock operation was not replicated. If a lossy failover occurs after the target mailbox was unlocked, the target mailbox could remain inaccessible.
Error details: Mailbox changes failed to replicate. Database Database doesn't satisfy the constraint SecondCopy because the commit time DateTime isn't guaranteed by replication time <Date> <Time>.
Cause
A replication delay in the service occurred. This may prevent some post-migration cleanup tasks from taking effect immediately.
Resolution
The user may be unable to access the mailbox immediately after the migration is complete. As soon as replication is complete, the user will be able to access the mailbox. If the user continues to be unable to access the mailbox 60 minutes after the migration is complete, contact Microsoft 365 Support.
More information
Still need help? Go to Microsoft Community or the Microsoft Q&A.
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