Toltec and domain versus IP

[Matthew Smart]

Hi there!

I have a new problem when connecting using pop/smtp through toltec connector.

If I specify the internal network IP of my server, and try to connect
using pop/smtp, it all works. When I try connecting using
mail.mydomain.com, it doesn't get a response from the server. I know
my router is set up correctly, and on the machine itself I can 'telnet
localhost 25' and 'telnet mail.mydomaincom.com' without any problems.
Any suggestions? I'm thinking it's a setting in main.cf, but I don't
know which one.

Thanks for any help,

Matthew Smart