Unable to Migrate mailbox to Office 365 - Source Mailbox Already being Moved
When migrating a mailbox from on premises Exchange Server to Office 365, it failed with below error message.
Transient error SourceMailboxAlreadyBeingMovedTransientException has occurred. The system will retry (1/620).
Restarted the Microsoft Exchange Mailbox Replication service and resumed the mailbox move - the mailbox was moved successfully.