I am just beginning to learn how to use iptables as a firewall for one
of my servers. In doing so, I have run into a bit of a roadblock that
I hope I can get some assistance with. The server that I am working
with acts as a DNS. At this point, clients are able to make DNS
requests to this server and get a proper response. However, the server
is unable to make DNS queries to other servers. Here is what I have in
my iptables:

iptables -A INPUT -i eth0 -p UDP --dport domain -m state --state
NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -i eth0 -p TCP --dport domain -m state --state
NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p UDP --sport domain -m state --state
NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p TCP --sport domain -m state --state
NEW,ESTABLISHED -j ACCEPT

What am I missing here?