RFC 2821 (rfc2821) - Page 1 of 79
Simple Mail Transfer Protocol
Alternative Format: Original Text Document
Network Working Group J. Klensin, Editor
Request for Comments: 2821 AT&T Laboratories
Obsoletes: 821, 974, 1869 April 2001
Updates: 1123
Category: Standards Track
Simple Mail Transfer Protocol
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.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document is a self-contained specification of the basic protocol
for the Internet electronic mail transport. It consolidates, updates
and clarifies, but doesn't add new or change existing functionality
of the following:
- the original SMTP (Simple Mail Transfer Protocol) specification of
RFC 821 [30],
- domain name system requirements and implications for mail
transport from RFC 1035 [22] and RFC 974 [27],
- the clarifications and applicability statements in RFC 1123 [2],
and
- material drawn from the SMTP Extension mechanisms [19].
It obsoletes RFC 821, RFC 974, and updates RFC 1123 (replaces the
mail transport materials of RFC 1123). However, RFC 821 specifies
some features that were not in significant use in the Internet by the
mid-1990s and (in appendices) some additional transport models.
Those sections are omitted here in the interest of clarity and
brevity; readers needing them should refer to RFC 821.
Klensin Standards Track