RFC 1651 · DRAFT STANDARD · 1994
MON · 27 JUL 2026
SMTP Service Extensions
Overview
RFC 1651, “SMTP Service Extensions”, is a Draft Standard document published in July 1994 by J. Klensin, N. Freed, M. Rose, E. Stefferud, D. Crocker. It obsoletes RFC 1425. It has been obsoleted by RFC 1869 — refer to the newer document for the authoritative version. The canonical text is published by the RFC Editor.
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. [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.
Read this RFC
The canonical text of RFC 1651 is hosted at rfc-editor.org. Available in TXT,HTML.
Relationships to other RFCs
Other RFCs from 1994
- RFC 1650 Definitions of Managed Objects for the Ethernet-like Interface Types using SMIv2
- RFC 1652 SMTP Service Extension for 8bit-MIMEtransport
- RFC 1649 Operational Requirements for X.400 Management Domains in the GO-MHS Community
- RFC 1653 SMTP Service Extension for Message Size Declaration
- RFC 1648 Postmaster Convention for X.400 Operations
- RFC 1654 A Border Gateway Protocol 4
- RFC 1647 TN3270 Enhancements
- RFC 1655 Application of the Border Gateway Protocol in the Internet