Here's a little more testing results using the Windows netstat command. 64.151.83.185 and 64.151.98.20 are both IP addresses on the same server hosting the gossamer mail application. 69.21.29.243 is an IP address outside the firewall. You can see that I am able to establish a connection through the firewall. For some reason the pop_server plugin doesn't respond over TCP when a connection is established. I am able to see that it works from a command prompt as I noted above. I think something is wrong in the way it's trying to connect to the standard I/O on Windows. Keep in mind that this system doesn't have inetd functionality. It's running under IIS6 with ActiveState Perl. It is not running under an Apache server on Windows.

Proto Local Address Foreign Address State
TCP 0.0.0.0:8110 0.0.0.0:0 LISTENING
TCP 64.151.83.185:8110 69.21.29.243:63412 ESTABLISHED
TCP 64.151.98.20:8110 64.151.98.20:3527 TIME_WAIT