We have a 2003 Exchange server and we are recieving the following bounce back when sending mail to a particular external mail server.
"The following recipient(s) could not be reached:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<SERVER.domain.local #5.5.0 smtp;501 <SERVER.domain.local> is invalid or DNS says does not exist>
Any help on this would be greatly appreciated and further information will be on hand.