Post Office Protocol - Version 3
RFC 1725
Document | Type |
RFC - Internet Standard
(November 1994; Errata)
Obsoleted by RFC 1939
Obsoletes RFC 1460
Was draft-rose-pop3-again (individual)
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Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text pdf html bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1725 (Internet Standard) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. Myers Request for Comments: 1725 Carnegie Mellon Obsoletes: 1460 M. Rose Category: Standards Track Dover Beach Consulting, Inc. November 1994 Post Office Protocol - Version 3 Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Overview This memo is a revision to RFC 1460, a Draft Standard. It makes the following changes from that document: - removed text regarding "split-UA model", which didn't add anything to the understanding of POP - clarified syntax of commands, keywords, and arguments - clarified behavior on broken connection - explicitly permitted an inactivity autologout timer - clarified the requirements of the "exclusive-access lock" - removed implementation-specific wording regarding the parsing of the maildrop - allowed servers to close the connection after a failed authentication command - removed the LAST command - fixed typo in example of TOP command - clarified that the second argument to the TOP command is non- negative - added the optional UIDL command Myers & Rose [Page 1] RFC 1725 POP3 November 1994 - added warning regarding length of shared secrets with APOP - added additional warnings to the security considerations section 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 is used to allow a workstation to retrieve mail that the server is holding for it. 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 This memo does not specify how a client host enters mail into the transport system, although a method consistent with the philosophy of this memo is presented here: When the user agent on a client host wishes to enter a message into the transport system, it establishes an SMTP connection to its relay host (this relay host could be, but need not be, the POP3 server host for the client host). 3. Basic Operation Initially, the server host starts the POP3 service by listening on TCP port 110. When a client host wishes to make use of the service, it establishes a TCP connection with the server host. When the connection is established, the POP3 server sends a greeting. The client and POP3 server then exchange commands and responses Myers & Rose [Page 2] RFC 1725 POP3 November 1994 (respectively) until the connection is closed or aborted. Commands in the POP3 consist of a keyword, possibly followed by one or more arguments. All commands are terminated by a CRLF pair. Keywords and arguments consist of printable ASCII characters. Keywords and arguments are each separated by a single SPACE character. Keywords are three or four characters long. Each argument may be up to 40 characters long. Responses in the POP3 consist of a status indicator and a keyword possibly followed by additional information. All responses are terminated by a CRLF pair. There are currently two status indicators: positive ("+OK") and negative ("-ERR"). Responses to certain commands are multi-line. In these cases, whichShow full document text