Post Office Protocol - Version 3 (RFC1460)
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2019-Feb-10
Internet Society Requests For Comment (RFCs)
This memo is a revision to RFC 1225, a Draft Standard. [STANDARDS-TRACK]
Network Working Group M. Rose Request for Comments: 1460 Dover Beach Consulting, Inc. Obsoletes: 1225 June 1993
Post Office Protocol - Version 3
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.
This memo is a revision to RFC 1225, a Draft Standard. It makes the following changes from that document:
- the RPOP facility is removed;
- the optional APOP facility is added (which is in interoperable, operational use in at least three implementations);
- a typo was corrected with respect to the interaction of LAST and RSET;
- section numbers were added; and,
- an acknowledgements section was added.
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
Rose [Page 1]
RFC 1460 POP3 June 1993
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).
If this method is followed, then the client host appears to the MTS as a user agent, and should NOT be regarded as a "trusted" MTS entity in any sense whatsoever. This concept, along with the role of the POP3 as a part of a split-UA model is discussed later in this memo.
3. Basic Operation
Initially, the server host starts the POP3 service by listening on TCP port 110. Wh...