Simple Mail Transfer Protocol
draft-ietf-emailcore-rfc5321bis-00
EMAILCORE J. Klensin
Internet-Draft October 6, 2020
Obsoletes: 5321, 1846, 7504 (if
approved)
Updates: 1123 (if approved)
Intended status: Standards Track
Expires: April 9, 2021
Simple Mail Transfer Protocol
draft-ietf-emailcore-rfc5321bis-00
Abstract
This document is a specification of the basic protocol for Internet
electronic mail transport. It consolidates, updates, and clarifies
several previous documents, making all or parts of most of them
obsolete. It covers the SMTP extension mechanisms and best practices
for the contemporary Internet, but does not provide details about
particular extensions. Although SMTP was designed as a mail
transport and delivery protocol, this specification also contains
information that is important to its use as a "mail submission"
protocol for "split-UA" (User Agent) mail reading systems and mobile
environments. This document replaces the earlier version with the
same title in RFC 5321.
[[CREF1: Note in Draft: Except for the last sentence, the above is
unchanged from 5321 and may need adjusting in the light of RFC 6409
as an Internet Standard.]]
Note on Reading This Working Draft
This working draft is extensively annotated with information about
changes made over the decade since RFC 5321 appeared, especially when
those changes might be controversial or should get careful review.
Anything marked in CREF comments with "[5321bis]" is current. In
general, unless those are marked with "[[Note in Draft", in the
contents of an "Editor's note", or are in the "Errata Summary"
appendix (Appendix H.1, they are just notes on changes that have
already been made and where those changes originated. Comments
identified as "2821ter" arose after the Last Call on what became
RFC5321, sometimes before AUTH48 on that document or a bit later.
Those, of course, should still be reviewed. Surviving comments about
rfc5321bis-00 followed by a letter indicate intermediate working
versions of this draft and can be ignored unless the origin of
changes is important. As one can tell from the dates (when they are
given), this document has been periodically updated over a very long
period of time.
Klensin Expires April 9, 2021 [Page 1]
Internet-Draft SMTP October 2020
This evolving draft should be discussed on the ietf-smtp@ietf.org
list.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 9, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Transport of Electronic Mail . . . . . . . . . . . . . . 6
1.2. History and Context for This Document . . . . . . . . . . 6
1.3. Document Conventions . . . . . . . . . . . . . . . . . . 7
2. The SMTP Model . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Basic Structure . . . . . . . . . . . . . . . . . . . . . 8
2.2. The Extension Model . . . . . . . . . . . . . . . . . . . 10
2.2.1. Background . . . . . . . . . . . . . . . . . . . . . 10
2.2.2. Definition and Registration of Extensions . . . . . . 11
2.2.3. Special Issues with Extensions . . . . . . . . . . . 12
2.3. SMTP Terminology . . . . . . . . . . . . . . . . . . . . 12
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