POP - Post Office Protocol
POP2 and POP3 standards are incompatible, but almost everything is POP3 now
Allows MAC and PC users a nice GUI interface to their mail, which they like
Mailboxes are on a central server, like your VMS box
POP clients connect to the server and copy their mail to their local hard drive
POP locks you in to reading mail on the client
POP clients can send binary attachments
POP servers can be either single-threaded (MultiNet) or multi-threaded (PMDF, Indiana University)