Problem
You’ve initiated a mailbox move request from one mailbox database to another (cross a WAN link in this example) but noticed that the migration stops / halts with the StatusDetailStalledDueToSource_MailboxCapacityExceeded:
Suspending and resuming the migration does not restart the process.
Solution
While there are various reasons why the mailbox migration would halt, one of the things to try to restart the process is to identify the source server that hosts the mailbox and restart it. Once the source server has been restarted with the services back up for a while, review the status again and verify it is either displaying InitialSeeding or CopyingMessages:
