There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.
telnet popserver 110 -server will (or should) respond indicating that it is ready user username - server will tell you that a password is required pass usernames_password - server will tell you how many messages username has list - server will show you size of each message retr 1 - first message will be displayed quit
If the server does not respond, then pop is not enabled. Find it in /etc/inetd.conf, uncomment it, and then send a kill -1 to the inet daemon:
kill -1 `cat /etc/inetd.pid`
Got something to add? Send me email.