DNSWL Email Authentication Method Extension
draft-vesely-authmethod-dnswl-11

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Last updated 2019-10-15
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IETF                                                           A. Vesely
Internet-Draft                                          October 15, 2019
Intended status: Informational
Expires: April 17, 2020

              DNSWL Email Authentication Method Extension
                    draft-vesely-authmethod-dnswl-11

Abstract

   This document describes an additional Email Authentication Method
   compliant with RFC 8601.  The method consists in looking up the
   sender's IP address in a DNS whitelist.

   This document does not consider black lists.

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 April 17, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Method Details  . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  TXT Record Contents . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     5.1.  Security of DNSSEC Validation . . . . . . . . . . . . . .   6
     5.2.  Inherited Security Considerations . . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Example  . . . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   One of the many checks that mail servers carry out is to query DNS
   whitelists (DNSWL, [RFC5782]).  The lookup is based on the connecting
   client's IP address, so this check can occur very early in an SMTP
   transaction.  The result can be used to counterweight policies that
   typically occur at early stages too, such as the Sender Policy
   Framework (SPF, the last paragraph of Appendix D.3 of [RFC7208] is
   illustrated in Appendix A).  In addition, the result of a DNSWL
   lookup can also be used at later stages; for example, a delivery
   agent can use it to learn the trustworthiness of a mail relay in
   order to estimate the spamminess of an email message.  The latter
   possibility needs a place to collect query results for downstream
   use, which is precisely what the Authentication-Results header field
   aims at providing.

   Results often contain additional data, encoded according to DNSWL-
   specific criteria.  The present method considers only whitelists
   --one of the major branches considered by [RFC5782].  In case of
   DNSxL, the boundary MTA (see [RFC5598]) which carries out the check
   and possibly stores the result, has to be able to discern at least
   the color of "x", which is required to make accept/reject decisions.
   The present method can then be used only if the DNSxL record to be
   reported turns out to be a whitelisting one.

   Data conveyed in A and TXT records can be stored as method's
   properties.  In effect, they are tantamount to local policies, albeit
   outsourced.  Downstream agents need to know DNSWL-specific encoding
   to understand the meaning of that data.  In order to smooth
   operations, this document endorses a usage of TXT fields consistent
   with other authentication methods.  Namely, to serve the domain name
   in the TXT record.

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