RFC 3459 · PROPOSED STANDARD · 2003

Critical Content Multi-purpose Internet Mail Extensions Parameter

Overview

RFC 3459, “Critical Content Multi-purpose Internet Mail Extensions Parameter”, is a Proposed Standard document published in January 2003 by E. Burger. It updates RFC 3204. It has since been updated by RFC 5621. The canonical text is published by the RFC Editor.

Abstract

This document describes the use of a mechanism for identifying body parts that a sender deems critical in a multi-part Internet mail message. The mechanism described is a parameter to Content-Disposition, as described by RFC 3204. By knowing what parts of a message the sender deems critical, a content gateway can intelligently handle multi-part messages when providing gateway services to systems of lesser capability. Critical content can help a content gateway to decide what parts to forward. It can indicate how hard a gateway should try to deliver a body part. It can help the gateway to pick body parts that are safe to silently delete when a system of lesser capability receives a message. In addition, critical content can help the gateway chose the notification strategy for the receiving system. Likewise, if the sender expects the destination to do some processing on a body part, critical content allows the sender to mark body parts that the receiver must process. [STANDARDS-TRACK]

Abstract as published in the RFC, via rfc-editor.org.

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 3459 is hosted at rfc-editor.org. Available in TXT,HTML.

Relationships to other RFCs
This RFC updates
RFC 3204
Updated by
RFC 5621
Other RFCs from 2003

Who Is Online

In total there are 64 users online: 0 registered, 56 guests and 8 bots.

Most users ever online was 5,555 on 17 Jul 2026, 3:23 am.

Bots: AhrefsBot Applebot Baiduspider Bingbot Majestic Other Bot PetalBot SemrushBot

Users active in the past 15 minutes. Total registered members: 372