We have started seeing all of our outgoing email backed up. Incoming and internal are fine. I did get an error on the queue of the exchange server that said read:
the pipleline has been stopped. It was runnng the command 'get-message 0resultSize '1000' -ReturnPageInfo $true -SortOrder' +FromAddress' -server "my servername.com' -SearchForward $true -bookmarkObject $null -BookmarkIndex '1' -Includebookmark $false -Filter '((Queue -eq "servername\submission'))"