Firewall with iptables and forwarding

[Linux <linux@worreby.ch>]

Hi

Have anybody a good recommendation for an easy to use firewall with port 
forwarding ?

I got a home network with a dedicated (Debian of course) firewall box with 
ADSL connected, and ipmasq package installed.

My problem is that I don't know HOW I should put in the various rules in 
ipmasq => Which makes me look for something simpler or some examples or tips.

What I want to do is open up for incoming mail and http to be able to access 
my mailserver and internal webserver from internet, but not necessarily on 
the standard ports but some other ones.

Any suggestions or recommendations ?

--Robert