[IP ?] what ip must be filtered ?

["Tanen" <tanen@tanen.dyndns.org>]

Hello,

I'm confused, i try to set up my Firewall, with iptables sure :)
The problem, an easy problem to solve for you, but a big for me, it's the
next :
I have an Dedicated server, Linux, on an internal local network, who have as
ip 192.168.0.1, and other puters have 192.168.0.2 *.3 *.4 etc ... BUT the
dedicated box, use the reuters of my connection to be connected to internet.
This reuters have as ip 192.168.0.100, and my external ip have as ip
63.*.*.*, my problem is to know, WHAT ip i must filter, to prevent of any
attack or hack, the reuters is forwarding the needed port (http,
pop/imap/smpt) to the dedicated box. All work fine sure. But what IP i must
filtered, and authorised for have my firewall working fine ? actualy when
i'm filtering my local ip, or my external ip, my mail server, isn't getting
any mail from www, someone can help me please ?

Thanks you.