HI,
I am assuming that you are setup behind
a router/firewall. You need to go into the
router configuration and set it to forward
ports 25 for smtp and 110 for pop3 to
the ip address of your server.
In some cases like the netgear rt314,
you also have to telnet to the router
ip and enable those ports as they
are disabled by default.
Just look in your router manual on how
to do this and you will be fine.
Scott.