IPTables Newbie

[Michael White]

Hello All,

I'm new to LUG's, so I haven't had time to search the archives for this or a similar question.  Please bear w/ me if I'm repeating a recently answered question as I'm in need of a quick resolution.

I'm building an RH9 firewall/mailserver combo box for a small client.  Sendmail appears to be running correctly in that I'm able to telnet to port 25 from an internal system.  However, after performing the following commands, I'm unable to telnet to the same port from and external IP:

IPTABLES -A INPUT -p tcp --dport 25 -j ACCEPT
IPTABLES -A INPUT -p ucp --dport 25 -j ACCEPT

Am I going about this all wrong?  Should I be entering the command differently?
Because this client is basically has no budget, running the firewall and the mailserver on the same box is my only option.  Any suggestions for resolving this problem are greatly appreciated?

TIA,
Michael White