Hi, I have a sendmail box that virus scans messages and then passes it on to one of 3 places:
1. Itself for one domain
2. A GroupWise server for students
3. Another GroupWise server for staff
However, if an outside user sends a message to an incorrect address on the Groupwise servers, the sender never gets a bounce back to say that the message couldn't be delivered. Which is rather anoying because they then think they have the right address.
An example: mail to email@example.com will bounce back ok as warr.ac.uk is local to the Sendmail box;
However, firstname.lastname@example.org will not bounce back as the message has been passed to Groupwise.
Now watching the mail on the Groupwise system, I can see that the Groupwise system bounces it with an undeliverable message, but the message either never gets accepted by Sendmail or is recieved but not passed on to the original sender.