Had an issue where Unity stopped forwarding voicemails from external callers to the appropriate user's mailboxes but internal msgs were reaching mailboxes fine. For both, mwi was not working. After failing over to the secondary server & rebooting the primary, all the messages were delivered & mwi worked again. Any idea why this would happen & or how this can be monitored. Apparently no one was getting their external voicemails for around a week & I didn't know there was an issue until someone mentioned it.