Email Greylisting: An Applicability Statement for SMTP
draft-ietf-appsawg-greylisting-06

The information below is for an old version of the document
Document Type Active Internet-Draft (appsawg WG)
Last updated 2012-04-13 (latest revision 2012-03-25)
Replaces draft-kucherawy-greylisting-bcp
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication
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Document shepherd Alexey Melnikov
Shepherd write-up Show (last changed 2012-03-30)
IESG IESG state IESG Evaluation
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Needs 5 more YES or NO OBJECTION positions to pass.
Responsible AD Barry Leiba
Send notices to appsawg-chairs@tools.ietf.org, draft-ietf-appsawg-greylisting@tools.ietf.org
Individual submission                                       M. Kucherawy
Internet-Draft                                                 Cloudmark
Intended status: Standards Track                              D. Crocker
Expires: September 26, 2012                  Brandenburg InternetWorking
                                                          March 25, 2012

         Email Greylisting: An Applicability Statement for SMTP
                   draft-ietf-appsawg-greylisting-06

Abstract

   This memo describes the art of email greylisting, the practice of
   providing temporarily degraded service to unknown email clients as an
   anti-abuse mechanism.

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
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   This Internet-Draft will expire on September 26, 2012.

Copyright Notice

   Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Background . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Types of Greylisting . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Connection-Level Greylisting . . . . . . . . . . . . . . .  4
     2.2.  SMTP HELO/EHLO Greylisting . . . . . . . . . . . . . . . .  5
     2.3.  SMTP MAIL Greylisting  . . . . . . . . . . . . . . . . . .  5
     2.4.  SMTP RCPT Greylisting  . . . . . . . . . . . . . . . . . .  5
     2.5.  SMTP DATA Greylisting  . . . . . . . . . . . . . . . . . .  6
     2.6.  Additional Heuristics  . . . . . . . . . . . . . . . . . .  7
     2.7.  Exceptions . . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Benefits and Costs . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Unintended Consequences  . . . . . . . . . . . . . . . . . . .  8
     4.1.  Unintended Mail Delivery Failures  . . . . . . . . . . . .  9
     4.2.  Unintended SMTP Client Failures  . . . . . . . . . . . . . 10
     4.3.  Address Space Saturation . . . . . . . . . . . . . . . . . 11
   5.  Recommendations  . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  Measuring Effectiveness  . . . . . . . . . . . . . . . . . . . 13
   7.  IPv6 Applicability . . . . . . . . . . . . . . . . . . . . . . 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
     9.1.  Tradeoffs  . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.2.  Database . . . . . . . . . . . . . . . . . . . . . . . . . 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     10.2. Informative References . . . . . . . . . . . . . . . . . . 15
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16

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1.  Introduction

   Preferred techniques for handling email abuse explicitly identify
   good actors and bad actors, giving each significantly differential
   service.  In some cases an actor does not have a known reputation;
   this can justify providing degraded service, until there is a basis
   for provider better service.  This latter approach is known as
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