A Registry for SMTP Enhanced Mail System Status Codes
The specification for enhanced mail system status codes, RFC 3463, establishes a new code model and lists a collection of status codes. While it anticipated that more codes would be added over time, it did not provide an explicit mechanism for registering and tracking those codes. This document specifies an IANA registry for mail system enhanced status codes, and initializes that registry with the codes so far established in published standards-track documents, as well as other codes that have become established in
What it is
The IANA registry of enhanced mail system status codes, and the process for adding one.
What it solves
RFC 3463 defined the shape of the codes. Something had to hold the authoritative list as it grew.
What it means to operate
This registry is the source of the enhanced codes in the SMTP reference on this site. If a code you are looking at is not in it, it is a provider's private extension, and you should read the provider's documentation rather than infer meaning from the number.
Normative requirements
This document does not use the RFC 2119 keywords. It states its requirements in ordinary prose, which is why nothing is listed here rather than because nothing was found.