May you know the http://p3scan.sourceforge.net/
project. It is a transperent pop3 proxy which use iptables to redirect tcp packets to port 8110 and run virus scanning. This port is p3scan own. The readme say: in the default case we can use the next iptables rule: "iptables -t nat -A PREROUTING -p tcp -i eth0 --dport pop3 -j REDIRECT --to 8110" and it's works fine when a packet coming from some clients from our local network. But I want to set up an another iptables rule, which say the next: if our linux gw (the p3scan runing on this server too) want to download our mails so that will be redirect to the port 8110 too.
thanks your help!