[ILUG] dns problem

[Declan Grady]

Hi,
I need some help.
I have a debian woody firewall running caching only nameserver (bind9).
outside world is on eth1, and local lan on eth0
I also have a redhat7 mailserver on the eth0 lan.

Most things seem to be working ok, but ...
I currently have a load of email (well, not a load, only about 20 or so) 
backed up
 for one destination domain, and mailq tells me ' host name lookup failure'

However, if I go to the firewall, and  'dig' that domain it does resolve ok.

I dont have dig or nslookup on the mailserver, so cannot  do the same 
dig/nslookup there.

on the mailserver, my  /etc/resolv.conf reads :
-----------------------------
domain
nameserver 192.168.x.x
---------------------------
where 192.168.x.x is the IP of the firewall

Routing seems ok, and fetchmail works from the mailserver to get my odmr 
email ok. (also using dns to resolve the hostname)
Incoming mail seems ok .. some dns failures for the same domain name I 
have problems sending to ... possibly an error in the config of that 
domain's dns 'setup' ?

How do I go about finding what the problem is ?

Thanks,
Declan