I had a similar problem - took a very long time to establish connections
from outside my own network. It turned out to be DNS-related. Basically, I
only allow specific ports through the router, and deny everything else. i.e.
I allow ports 22,25,110
What I had to do was to allow packets with the ACK bit set to pass on other
ports i.e. the connection is established, and a port is negotiated for the
server and client to talk on. The server then continues listening on the
default SMTP and POP3 ports.
