After runnning exchange best practices tool, they told me to go to
http://www.microsoft.com/technet/prodtechnol/exchange/Analyzer/2582b127-b826-4eac-88b6-47a79ed49c6d.mspx
to fix the error reporting problem. I did so & then no-one could send emails
(disabled it & shock horror -> people can send emails again). The error I was
getting when trying to send the emails was " A configuration error in the
e-mail system caused the message to bounce between two servers or to be
forwarded between two recipients".
This is really interesting as we have only one server as well. Anybody want
to input or Microsoft want to explain please....

Thanks

Exhange send permissions
Technical reasons to consolidate a distributed E2K3 Org ?
Change Message-ID portion of outgoing emails?
Move e-mail before removing account. Exch 2003
SMTP address.