Hi,

looking at most documentation I should use this in /etc/hosts

127.0.0.1 localhost.localdomain localhost
192.168.0.10 mybox.mydomain.com mybox


but what if that server is also a mail server that has a DNS entry of mail.mydomain.com??

should it now read...

127.0.0.1 localhost.localdomain localhost
192.168.0.10 mybox.mydomain.com mybox mail.mydomain.com mail


thanks for looking at this, any input is much appreciated

Follow this guide to properly set the hostname.
The hostname MUST be set correctly for a mail server or it will cause problems.
I found out the hard way what sort of trouble a small hostname error will cause your mail server, everything else was right, but the hostname wasn't set properly in every location. That landed my legit mailserver on a blacklist..

http://www.cpqlinux.com/hostname.html

Thanks, that was really helpful.

I still don't quite understand something though. I've seen it written in several places that the local hostname doesn't/shouldn't be the same as the DNS name - so I might call it 'mybox' locally but 'mail'... on the DNS.

This is fine, but if I add a certificate then it has to have the same name (common name) as the server does locally or else it throws up warnings, but the user is connecting via the DNS name. So how does that work? Or have I just got the wrong end of the stick??

Well wherever you read that it is incorrect. the local hostname set on the mail server needs to be the SAME as the public registered DNS name. That is what caused the problem for me. the DNS name registered for the machine was mail.mydomain.com but the hostname was being reported as something slightly different so when the other mail server got the HELO message and did the lookup, the local hostname reported by my server was different than the DNS name it didn't match and their server automatically submitted my machine to one of the blacklists..

It is true that you can set them differently but in the case of a mail server. the mail server had better respond in the HELO with a name that matches one registered in the public DNS.

ok, thanks, that was really helpful.