We're seeing some mailboxes getting the following returned to the senders:
The server has tried to deliver this message, without success, and has stopped trying. Please try sending this message again. If the problem continues, contact your helpdesk.
Diagnostic information for administrators:
Generating server: FCCAMEXCH02.uk.fc.local
It's happening to few random mailboxes and I can't understand why..how. Before restarting anything, are there any diagnostic checks that you would make?