SMTP 521 and 556 Reply Codes
RFC 7504
Document | Type |
RFC - Proposed Standard
(June 2015; No errata)
Was draft-klensin-smtp-521code (individual in app area)
|
|
---|---|---|---|
Author | John Klensin | ||
Last updated | 2015-10-14 | ||
Replaces | draft-klensin-rfc1846bis | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | Tony Hansen | ||
Shepherd write-up | Show (last changed 2015-03-05) | ||
IESG | IESG state | RFC 7504 (Proposed Standard) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Barry Leiba | ||
Send notices to | ietf-smtp@ietf.org | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | RFC-Ed-Ack |
Internet Engineering Task Force (IETF) J. Klensin Request for Comments: 7504 June 2015 Updates: 1846, 5321 Category: Standards Track ISSN: 2070-1721 SMTP 521 and 556 Reply Codes Abstract This memo defines two Simple Mail Transfer Protocol (SMTP) reply codes, 521 and 556. The 521 code was originally described in an Experimental RFC in 1995 and is in wide use, but has not previously been formally incorporated into SMTP. The 556 code was created to support the new tests and actions specified in RFC 7505. These codes are used to indicate that an Internet host does not accept incoming mail at all. This specification is not applicable when the host sometimes accepts mail but may reject particular messages, or even all messages, under specific circumstances. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7504. Klensin Standards Track [Page 1] RFC 7504 SMTP 521 and 556 Reply Codes June 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The 521 Reply Code . . . . . . . . . . . . . . . . . . . . . 4 4. The 556 Reply Code . . . . . . . . . . . . . . . . . . . . . 4 5. Small Details to Avoid Loose Ends . . . . . . . . . . . . . . 5 5.1. Specific Changes to RFC 5321 . . . . . . . . . . . . . . 5 5.2. The RFC 1846 Experiment . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 Klensin Standards Track [Page 2] RFC 7504 SMTP 521 and 556 Reply Codes June 2015 1. Introduction The SMTP specification [2] (referred to, along with its various updates, as "SMTP" below) contains a list and discussion of reply codes. This document updates that list with a new code, 521, for use in response to an initial connection. In that context, it specifically denotes a system that does not receive mail or otherwise handle SMTP mail or inquiry transactions. That code differs from the use of reply code 554, recommended by RFC 5321, because the latter code can be used in a larger variety of situations, including mail that is not accepted for, or from, particular sources, destinations, or addresses. It also introduces a second reply code, 556, for use when an SMTP client encounters a domain in a forward-pointing address that it can determine (e.g., from the DNS "null MX" convention [5]) does not support receipt of mail and has to report that condition to a host that delivered the message to it for further processing. This specification updates RFC 5321 to add the new codes. The 521 code was first formally proposed in the Experimental RFC 1846 [4]; this document updates that specification to standardize the code and provide more specific treatment of it. 1.1. Terminology The reader of this document is expected to have reasonable familiarity with the SMTP specification in RFC 5321, particularly itsShow full document text