RFC 1425 · PROPOSED STANDARD · 1993
TUE · 28 JUL 2026
SMTP Service Extensions
Overview
RFC 1425, “SMTP Service Extensions”, is a Proposed Standard document published in February 1993 by J. Klensin, N. Freed, M. Rose, E. Stefferud, D. Crocker. It has been obsoleted by RFC 1651 — 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 “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
Read this RFC
The canonical text of RFC 1425 is hosted at rfc-editor.org. Available in TXT,HTML.
Relationships to other RFCs
Other RFCs from 1993
- RFC 1424 Privacy Enhancement for Internet Electronic Mail: Part IV: Key Certification and Related Services
- RFC 1426 SMTP Service Extension for 8bit-MIMEtransport
- RFC 1423 Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers
- RFC 1427 SMTP Service Extension for Message Size Declaration
- RFC 1422 Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management
- RFC 1428 Transition of Internet Mail from Just-Send-8 to 8bit-SMTP/MIME
- RFC 1421 Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures
- RFC 1429 Listserv Distribute Protocol