RFC 1651 (rfc1651) - Page 1 of 11
SMTP Service Extensions
Alternative Format: Original Text Document
Network Working Group J. Klensin, WG Chair
Request for Comments: 1651 MCI
Obsoletes: 1425 N. Freed, Editor
Category: Standards Track Innosoft
M. Rose
Dover Beach Consulting, Inc.
E. Stefferud
Network Management Associates, Inc.
D. Crocker
Silicon Graphics, Inc.
July 1994
SMTP Service Extensions
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.
1. Abstract
This memo defines a framework for extending the SMTP service by
defining a means whereby a server SMTP can inform a client SMTP as to
the service extensions it supports. Standard extensions to the SMTP
service are registered with the IANA. This framework does not
require modification of existing SMTP clients or servers unless the
features of the service extensions are to be requested or provided.
2. Introduction
The Simple Mail Transfer Protocol (SMTP) [1] has provided a stable,
effective basis for the relay function of message transfer agents.
Although a decade old, SMTP has proven remarkably resilient.
Nevertheless, the need for a number of protocol extensions has become
evident. Rather than describing these extensions as separate and
haphazard entities, this document enhances SMTP in a straightforward
fashion that provides a framework in which all future extensions can
be built in a single consistent way.
3. Framework for SMTP Extensions
For the purpose of service extensions to SMTP, SMTP relays a mail
object containing an envelope and a content.
Klensin, Freed, Rose, Stefferud & Crocker