DNSWL Email Authentication Method Extension
draft-vesely-authmethod-dnswl-04

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IETF                                                           A. Vesely
Internet-Draft
Intended status: Informational                             April 4, 2016
Expires: October 6, 2016

              DNSWL Email Authentication Method Extension
                    draft-vesely-authmethod-dnswl-04

Abstract

   This document describes an additional Email Authentication Method
   compliant with RFC 7601.  The method consists in looking up the
   sender'IP in a DNS whitelist.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on October 6, 2016.

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   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Method Details  . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Example  . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

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, see in particular the last paragraph of Appendix D.3
   of [RFC7208]).  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".  It is required to make accept/reject decisions.

   Additional data can be stored as result's parameters.  In effect,
   they are tantamount to local policies, albeit outsourced.  Downstream
   agents can take advantage of DNSWL-specific knowledge to make finer
   decisions, such as render additional information or deliver to
   apposite folders.

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.

   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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               different name.  The name stored here has to be the best
               available reference for all foreseable downstream
               consumers.

   policy.ip:  The bit mask value received in type A response, in dotted
               quad.  This entry can be repeated if the DNSWL returns
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