RFC 4021 · PROPOSED STANDARD · 2005
MON · 27 JUL 2026
Registration of Mail and MIME Header Fields
Overview
RFC 4021, “Registration of Mail and MIME Header Fields”, is a Proposed Standard document published in March 2005 by G. Klyne, J. Palme. It has since been updated by RFC 5322. The canonical text is published by the RFC Editor.
Abstract
This document defines the initial IANA registration for permanent mail and MIME message header fields, per RFC 3864. [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 4021 is hosted at rfc-editor.org. Available in TXT,HTML.
Relationships to other RFCs
Other RFCs from 2005
- RFC 4020 Early IANA Allocation of Standards Track Code Points
- RFC 4022 Management Information Base for the Transmission Control Protocol
- RFC 4019 RObust Header Compression : Profiles for User Datagram Protocol Lite
- RFC 4023 Encapsulating MPLS in IP or Generic Routing Encapsulation
- RFC 4018 Finding Internet Small Computer Systems Interface Targets and Name Servers by Using Service Location Protocol version 2
- RFC 4024 Voice Messaging Client Behaviour
- RFC 4017 Extensible Authentication Protocol Method Requirements for Wireless LANs
- RFC 4025 A Method for Storing IPsec Keying Material in DNS