Newbie request

[Nandan Bhat <nlbhat@gmail.com>]

Hi,

I am trying to setup an old machine having two NICs with Fedora Core 5.
I have two Class C networks (I hope I got that right).
eth0 is assigned 192.168.1.6/255.255.255.0 .
eth1 is set to DHCP and is part of 192.168.0.0/24 .

I need some machines on 192.168.1.0/24 network to be able to get/send 
mail using 192.168.0.10 . Mail is limited to these networks and does not 
go to the outside world.
I have gone through the Linux-IP-Masquerade HOWTO and feel that I don't 
need a very liberal ruleset. Only smtp,pop functionality, especially 
connecting with 192.168.0.10 is sufficient.
My question is: Do I need a SNAT rule or should I try something with 
nat+FORWARD? I just went through iptables manual and am somewhat able to 
understand the rules in the HOWTO - stronger firewall example.
Thanks in advance,

Nandan Bhat