We are having a problem sending emails to one domain, bt.com. When we send an email to anyone at bt.com we receive the following bounce back
The message cannot be delivered due to a configuration error on the server. Please contact your Administrator.
< *.*.com #5.3.0>
We have not changed anything on our systems, we are currently running exchange 2003, and MIMEsweeper for SMTP Version 5.0.
I have no idea what to do, I currently set up a reverse dns entry after the error occured, and I can't get through to anyone at bt. Could anyone else sugegst anything?