We use port 110 on the local network and a random high port externally.

The internet gateway 'port forwards' this high external port to port 110 on the mail server so merc only needs to use one listening port. 

Is there a way to set an alternate port for Pop3 as there is for the SMTP server.  In other words, the normal port 25 would continue to work, but connections could also be accepted on an alternate port?

 TIA

R

You cannot setup two ports for MercuryP (POP3 server) as you can for MercuryS (SMTP server) but you can change the port number from the default (110) if you want / need to.  This is done via the "Listen on TCP port" option under the MercuryP POP3 Server configuration menu.

Lex 

Found an application that might do what you want.

 http://www.greyware.com/software/detour/