http://www.ietf.org/rfc/rfc2384.txt
[POP3] is a widely-deployed mail access protocol. Many programs access POP3 message stores, and thus need POP3 configuration information. Since there are multiple configuration elements which are required in order to access a mailbox, a single string representation is convenient.

A POP3 mailbox (like an [IMAP4] mailbox) is a network resource, and URLs are a widely-supported generalized representation of network resources.

A means of specifying a POP3 mailbox as a URL will likely be useful in many programs and protocols. [ACAP] is one case where a string encapsulation of elements required to access network services is needed. For example, an [IMAP4] message store is usually specified in ACAP datasets as an [IMAP-URL].

This memo defines a URL scheme for referencing a POP mailbox.