A NULL MX Resource Record for Domains that Accept No Mail
draft-ietf-appsawg-nullmx-00

The information below is for an old version of the document
Document Type Active Internet-Draft (appsawg WG)
Authors John Levine  , Mark Delany 
Last updated 2014-02-15
Replaces draft-delany-nullmx
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Intended RFC status Proposed Standard
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Network Working Group                                          J. Levine
Internet-Draft                                      Taughannock Networks
Intended status: Standards Track                               M. Delany
Expires: August 18, 2014                                      Apple Inc.
                                                       February 14, 2014

       A NULL MX Resource Record for Domains that Accept No Mail
                      draft-ietf-appsawg-nullmx-00

Abstract

   When the 5321.MailFrom domain in an e-mail message has a DNS MX
   Resource Record (RR), it is making an explicit statement that it is
   willing to accept email.  However, when the domain has just a DNS A
   or AAAA RR, there mail clients cannot easily tell whether the domain
   accepts mail, as many hosts on the Internet advertise an A or AAAA RR
   regardless of whether they want to accept email.

   The NULL MX RR formalizes the existing mechanism by which a domain
   announces that it accepts no mail.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on August 18, 2014.

Copyright Notice

   Copyright (c) 2014 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

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SMTP server benefits  . . . . . . . . . . . . . . . . . . . .   3
   3.  Parallel Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  The NULL MX Resource Record . . . . . . . . . . . . . . . . .   4
   5.  Domains that do not send mail . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Inforrmative References . . . . . . . . . . . . . . . . .   5
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   5
     A.1.  Change to appsawg-nullmx-0  . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   This document formally defines the "NULL MX" as a simple mechanism by
   which a domain can indicate that it will never accept email.

   SMTP clients have a prescribed sequence for resolving how to deliver
   email to a domain.  Section 5 of [RFC5321] covers this in detail, but
   in essence the SMTP client first looks up a DNS MX RR and if that is
   not found it falls back to looking up a DNS A or AAAA RR.

   Many domains do not accept email, but do have A or AAAA records.  If
   they have no MX records, senders will attempt to deliver mail to
   those A or AAAA records.

   If there is no SMTP listener at that address, the message will be
   attempted repeatedly for a long period, typically a week, before the
   sending MTA gives up.  This will delay notification to the sender in
   the case of misdirected mail, and will consume resources at the
   sender.

   If the domain has an SMTP listener at that address that rejects all
   connections (for instance with a 554 response as a connection-opening
   response) or has MX records pointing to such a listener then the
   sender will be notified in a timely fashion, but resources
   (generating a bounce) will still be consumed by the sender and it
   requires additional services to be provided which provide little
   benefit to the domain.

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   These resource usage problems are exacerbated when large volumes of
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