A NULL MX Resource Record for Domains that Accept No Mail
draft-ietf-appsawg-nullmx-03

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 2014-06-04
Replaces draft-delany-nullmx
Stream IETF
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: December 6, 2014                                     Apple Inc.
                                                            June 4, 2014

       A NULL MX Resource Record for Domains that Accept No Mail
                      draft-ietf-appsawg-nullmx-03

Abstract

   Internet mail determines the address of a receiving server through
   the DNS, first by looking for an MX record and then by looking for an
   A/AAAA record as a fallback.  Unfortunately this means that the A/
   AAAA record is taken to be mail server address even when that address
   does not accept mail.  The NULL MX RR formalizes the existing
   mechanism by which a domain announces that it accepts no mail, which
   permits significant operational efficiencies.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 6, 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must

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   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

   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  SMTP Server Benefits  . . . . . . . . . . . . . . . . . . . .   3
   4.  Parallel Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  The NULL MX Resource Record . . . . . . . . . . . . . . . . .   4
   6.  Domains that Do Not Send Mail . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Inforrmative References . . . . . . . . . . . . . . . . .   5
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   5
     A.1.  Change to appsawg-nullmx-03 . . . . . . . . . . . . . . .   5
     A.2.  Change to appsawg-nullmx-02 . . . . . . . . . . . . . . .   5
     A.3.  Change to appsawg-nullmx-1  . . . . . . . . . . . . . . .   6
     A.4.  Change to appsawg-nullmx-0  . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Introduction

   This document formally defines the "NULL MX" as a simple mechanism by
   which a domain can indicate that it does not accept email.

   SMTP clients have a prescribed sequence for identifying a server that
   accepts email for 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.
   Hence this overloads an email service semantic onto a DNS record with
   a different primary mission.

   If a domain has no MX records, senders will attempt to deliver mail
   to the hosts at the domain's A or AAAA record's addresses.  However
   many domains do not accept email.

   If there is no SMTP listener at the A/AAAA address, message delivery
   will be attempted repeatedly for a long period, typically a week,
   before the sending MTA gives up.  This will delay notification to the

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   sender in the case of misdirected mail, and will consume resources at
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