Hello,
In our University-net is the SMTP-Port closed for conexions from outside.
In our institut we used a firewall for security:
linux
2 Nics in promiscuous mode
brcfg (bridge)
transparent (without IP)
iptables
with portforwardings for webserver, mailserver, etc.
We dont use NAT, because our IP are external IPs.
rules are like:
iptables -A FORWARD -d 123.45.67.89 -p TCP --dport 80 -j ACCEPT
iptables -A FORWARD -d 123.45.67.89 -p TCP --dport 110 -j ACCEPT

I want the firewall to accept conexions in port 10025 (for example) and forward to port 25, so that we can configure our mail-client (at home) on another port.

is it posible?
thanxs

Ernesto