Which distribution do you use?
I'm using Fedora Core 4.
Also Falko (or anyone else) as per the first post, is there another reason why I get this in the returned email I send to my domain from an outside email address?
<firstname.lastname@example.org> (expanded from <email@example.com>): Host or domain name not found.
Name service error for name=www.www type=A: Host not found