I've been having several users randomly getting these bounce backs about an SMTP communication problem with the recipients email server, some say sorry, no mailbox here by that name, some say please turn on SMTP authentication in your mail client.
When tracking the message in the System Manager it never shows it leaves our Exchange server just gives the NDR.
I went to check the event logs and saw that there was a DCOM error 10009 saying it was unable to communicate with the computer abc.bigfish.com using any of the configured protocols.
Its interesting because the user can send it out again and it will eventually go.
So why is this happening and what could be causing it.