Simple Mail Transfer Protocol
RFC 5321, “Simple Mail Transfer Protocol”, is a Draft Standard document published in October 2008 by J. Klensin. It updates RFC 1123. It obsoletes RFC 2821. It has since been updated by RFC 7504. The canonical text is published by the RFC Editor.
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. [STANDARDS-TRACK]
What “Draft Standard” means
A historical maturity level (retired in 2011) that sat between Proposed Standard and Internet Standard and required multiple interoperable implementations.
The canonical text of RFC 5321 is hosted at rfc-editor.org. Available in TXT,HTML.
- RFC 5322 Internet Message Format
- RFC 5323 Web Distributed Authoring and Versioning SEARCH
- RFC 5318 The Session Initiation Protocol P-Refused-URI-List Private- Header
- RFC 5324 MIB for Fibre-Channel Security Protocols
- RFC 5325 Licklider Transmission Protocol - Motivation
- RFC 5316 ISIS Extensions in Support of Inter-Autonomous System MPLS and GMPLS Traffic Engineering
- RFC 5326 Licklider Transmission Protocol - Specification
- RFC 5327 Licklider Transmission Protocol - Security Extensions