Intermitent problems with outgoing email. get the event log message below
The Microsoft Exchange Mail Submission service is currently unable to contact any Hub Transport servers in the local Active Directory site. The servers may be too busy to accept new connections at this time.
Changed the Maximumconocurrent submissions from 30 to 50
did not help
when it happens tried restarting services on both Exchange server and domain controller
End up having to reboot the domain controller and thenn mail will flow