DNSWL Email Authentication Method Extension
draft-vesely-authmethod-dnswl-08

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Last updated 2019-05-20
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IETF                                                           A. Vesely
Internet-Draft                                              May 18, 2019
Intended status: Informational
Expires: November 19, 2019

              DNSWL Email Authentication Method Extension
                    draft-vesely-authmethod-dnswl-08

Abstract

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

   This document describes 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.

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   This Internet-Draft will expire on November 19, 2019.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Method Details  . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  TXT Record Contents . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Example  . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

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 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.

   Data conveyed in A and TXT records can be stored as result's
   parameters.  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.

2.  Method Details

   The following ptype.property items define the relevant parameters
   where additional data can be stored.  They augment the "pass" result
   with information about the entry found.

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   dns.zone:   DNSWL query root domain, which defines the meaning of the
               result.  Note that an MTA can use a local mirror with a
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