[CentOS] Could not connect to host box.domain.tld

I have used fetchmail/procmail/postfix/dovecot/kmail for some time on my mail server, and have set this up on three or four machines in the past. I'm now setting up a new server and having problems. I've reached the thinking-in-circles stage, so need a prompt.

The box in question is called borg2.lydgate.lan, and resides at 192.168.0.40. I can ping both borg2.lydgate.lan and 192.168.0.40, yet kmail tells me that it cannot connect to it, either by name or ip. /etc/hosts has correct lines for the box. It has to be something pretty basic, but I can't think what, unless it is either an selinux problem or ipv6 problem. I know that in FC6 I turned ipv6 off (I'd have to search to find how to do that again).

Anne