Advice for Safe Handling of Malformed Messages

The information below is for an old version of the document
Document Type Expired Internet-Draft (appsawg WG)
Authors Murray Kucherawy  , Gregory Shapiro
Last updated 2013-04-12 (latest revision 2012-10-09)
Replaces draft-kucherawy-mta-malformed
Stream Internet Engineering Task Force (IETF)
Expired & archived
pdf htmlized bibtex
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Stream WG state Parked WG Document
Document shepherd Salvatore Loreto
IESG IESG state Expired (IESG: Dead)
Consensus Boilerplate Unknown
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Responsible AD Barry Leiba
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The email ecosystem has long had a very permissive set of common processing rules in place, despite increasingly rigid standards governing its components, ostensibly to improve the user experience. The handling of these come at some cost, and various components are faced with decisions about whether or not to permit non-conforming messages to continue toward their destinations unaltered, adjust them to conform (possibly at the cost of losing some of the original message), or outright rejecting them. This document includes a collection of the best advice available regarding a variety of common malformed mail situations, to be used as implementation guidance. It must be emphasized, however, that the intent of this document is not to standardize malformations or otherwise encourage their proliferation. The messages are manifestly malformed, and the code and culture that generates them needs to be fixed. Therefore, these messages should be rejected outright if at all possible. Nevertheless, many malformed messages from otherwise legitimate senders are in circulation and will be for some time, and, unfortunately, commercial reality shows that we cannot always simply reject or discard them. Accordingly, this document presents alternatives for dealing with them in ways that seem to do the least additional harm until the infrastructure is tightened up to match the standards.


Murray Kucherawy (
Gregory Shapiro (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)