Network Working Group                                           J. Myers
Request for Comments: 1939                               Carnegie Mellon
STD: 53                                                          M. Rose
Obsoletes: 1725                             Dover Beach Consulting, Inc.
Category: Standards Track                                       May 1996


                    Post Office Protocol - Version 3

Status of this Memo(RFC1661に同じ)

1. Introduction

   On certain types of smaller nodes in the Internet it is often
   impractical to maintain a message transport system (MTS).  For
   example, a workstation may not have sufficient resources (cycles,
   disk space) in order to permit a SMTP server [RFC821] and associated
   local mail delivery system to be kept resident and continuously
   running.  Similarly, it may be expensive (or impossible) to keep a
   personal computer interconnected to an IP-style network for long
   amounts of time (the node is lacking the resource known as
   "connectivity").

   Despite this, it is often very useful to be able to manage mail on
   these smaller nodes, and they often support a user agent (UA) to aid
   the tasks of mail handling.  To solve this problem, a node which can
   support an MTS entity offers a maildrop service to these less endowed
   nodes.  The Post Office Protocol - Version 3 (POP3) is intended to
   permit a workstation to dynamically access a maildrop on a server
   host in a useful fashion.  Usually, this means that the POP3 protocol
   is used to allow a workstation to retrieve mail that the server is
   holding for it.

   POP3 is not intended to provide extensive manipulation operations of
   mail on the server; normally, mail is downloaded and then deleted.  A
   more advanced (and complex) protocol, IMAP4, is discussed in
   [RFC1730].

   For the remainder of this memo, the term "client host" refers to a
   host making use of the POP3 service, while the term "server host"
   refers to a host which offers the POP3 service.

2. A Short Digression(以下，略)

12. References

   [RFC821] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
       821, USC/Information Sciences Institute, August 1982.

   [RFC822] Crocker, D., "Standard for the Format of ARPA-Internet Text
       Messages", STD 11, RFC 822, University of Delaware, August 1982.

   [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
       MIT Laboratory for Computer Science, April 1992.

   [RFC1730] Crispin, M., "Internet Message Access Protocol - Version
       4", RFC 1730, University of Washington, December 1994.

   [RFC1734] Myers, J., "POP3 AUTHentication command", RFC 1734,
       Carnegie Mellon, December 1994.