Sieve Email Filtering: Reject and Extended Reject Extensions
RFC 5429

Network Working Group                                      A. Stone, Ed.
Request for Comments: 5429                                   Serendipity
Obsoletes: 3028                                               March 2009
Updates: 5228
Category: Standards Track

      Sieve Email Filtering: Reject and Extended Reject Extensions

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

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Abstract

   This memo updates the definition of the Sieve mail filtering language
   "reject" extension, originally defined in RFC 3028.

   A "Joe-job" is a spam run forged to appear as though it came from an
   innocent party, who is then generally flooded by automated bounces,
   Message Disposition Notifications (MDNs), and personal messages with

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RFC 5429                Sieve Extension: Reject               March 2009

   complaints.  The original Sieve "reject" action defined in RFC 3028
   required use of MDNs for rejecting messages, thus contributing to the
   flood of Joe-job spam to victims of Joe-jobs.

   This memo updates the definition of the "reject" action to allow
   messages to be refused during the SMTP transaction, and defines the
   "ereject" action to require messages to be refused during the SMTP
   transaction, if possible.

   The "ereject" action is intended to replace the "reject" action
   wherever possible.  The "ereject" action is similar to "reject", but
   will always favor protocol-level message rejection.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  3
   2.  Sieve "reject" and "ereject" Extensions  . . . . . . . . . . .  4
     2.1.  Action ereject . . . . . . . . . . . . . . . . . . . . . .  4
       2.1.1.  Rejecting a Message at the SMTP/LMTP Protocol Level  .  5
       2.1.2.  Rejecting a Message by Sending a DSN . . . . . . . . .  5
     2.2.  Action reject  . . . . . . . . . . . . . . . . . . . . . .  6
       2.2.1.  Rejecting a Message by Sending an MDN  . . . . . . . .  7
     2.3.  Silent Upgrade from "reject" to "ereject"  . . . . . . . .  8
     2.4.  Compatibility with Other Actions . . . . . . . . . . . . .  9
     2.5.  Details of Protocol-Level Refusal  . . . . . . . . . . . .  9
   3.  Changes from RFC 3028  . . . . . . . . . . . . . . . . . . . . 11
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     5.1.  "reject" Extension Registration  . . . . . . . . . . . . . 11
     5.2.  "ereject" Extension Registration . . . . . . . . . . . . . 12
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 14
   Appendix B.  Contributors  . . . . . . . . . . . . . . . . . . . . 14

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RFC 5429                Sieve Extension: Reject               March 2009