Port forwarding on a NAT firewall

["Antony" <antony@antgel.co.uk>]

Hi all,

If I have a router running iptables with NAT for a private IP network,
there are two options if I want to have a public email server on the
private network...
1) Set up an email server on the router that relays all mail to the
private server.2) Port forward (DNAT) port 25 to the private server.

I don't like port forwarding, as it's always seemed like a kind of bodge,
but (2) is quicker and easier to setup.  Does (2) have any practical
negative implications from a security point of view, and does anyone have
any general views on which solution is better?
A