Some of my users are sending email outside the company and receiving "
A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients.  Contact your administrator.            < #4.4.6>

I have a clustered Exchange 2k3 with an Exchange 2k3 front end. The system has been performing for years now this is happening. I have tested sending from my email (in the same domain as the user) and was successful. I have read KB316617 and have been told that the smtp connector is not the problem. My supervisor has tried that already. I can reboot the front end server and mail will be sent successfully for a while. It is also to multiple recipients not just one.