Gnu-pop3dS provides a modification of gnu-pop3d with dynamic forking incoming clients.
Gnu-pop3dS like SEMAPHORE, not SSL. If You need SSL use Gnu-pop3Sd (huge difference).
I used Gnu-pop3d, but it has a few failures. So I added some options to it.
I added option -D which converts mailpath "username"->"u/s/username" or "a"->"a/a/a".
Server is for users (NOT users for server), so I added option which controls number of connected users and forks next processes if we need them (man ipcs).
Many people asked me about SSL implementation. To do it get Stunnel and install it.
So You will have POP3S protocol implementation (works fine with all Microsoft gadgets).