POP3 server authentication
Location: POP3 server settings link in Administration > Users > Authentication
POP stands for Post Office Protocol. This is used to describe how e-mail clients
interact with mail servers. The POP3 Server is a type of mail server used for incoming
mail. In simple terms, POP servers provide a mail-drop service (a temporary mailbox to
leave messages so they can be picked up at the recipient's convenience.) When users
connect to their ISP POP servers, their e-mail software interface with the server and
download any messages for them. POP is only used to receive messages, it is not used to
send them. In computing, local e-mail clients use the Post Office Protocol version 3 (POP3), an
application-layer Internet standard protocol, to retrieve e-mail from a remote server
over a TCP/IP connection. Many subscribers to individual Internet service provider e-
mail accounts access their e-mail with client software that uses POP3.
http://moodle.org/mod/forum/discuss.php?d=9131 includes a problematic discussion on POP3 authentication.