Sieve Extension: Externally Stored Lists
RFC 6134

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Internet Engineering Task Force (IETF)                       A. Melnikov
Request for Comments: 6134                                 Isode Limited
Category: Standards Track                                       B. Leiba
ISSN: 2070-1721                                      Huawei Technologies
                                                               July 2011

                Sieve Extension: Externally Stored Lists

Abstract

   The Sieve email filtering language can be used to implement email
   whitelisting, blacklisting, personal distribution lists, and other
   sorts of list matching.  Currently, this requires that all members of
   such lists be hard-coded in the script itself.  Whenever a member of
   a list is added or deleted, the script needs to be updated and
   possibly uploaded to a mail server.

   This document defines a Sieve extension for accessing externally
   stored lists -- lists whose members are stored externally to the
   script, such as using the Lightweight Directory Access Protocol
   (LDAP), the Application Configuration Access Protocol (ACAP), vCard
   Extensions to WebDAV (CardDAV), or relational databases.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6134.

Copyright Notice

   Copyright (c) 2011 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect

Melnikov & Leiba             Standards Track                    [Page 1]
RFC 6134        Sieve Extension: Externally Stored Lists       July 2011

   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  3
   2.  Extlists Extension . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Capability Identifier  . . . . . . . . . . . . . . . . . .  3
     2.2.  :list Match Type for Supported Tests . . . . . . . . . . .  3
     2.3.  :list Tagged Argument to the "redirect" Action . . . . . .  5
     2.4.  Other Uses for External Lists  . . . . . . . . . . . . . .  5
     2.5.  Syntax of an Externally Stored List Name . . . . . . . . .  5
     2.6.  Definition of "addrbook" URN Parameter . . . . . . . . . .  7
     2.7.  Test valid_ext_list  . . . . . . . . . . . . . . . . . . .  9
     2.8.  Interaction with ManageSieve . . . . . . . . . . . . . . .  9
     2.9.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 10
       2.9.1.  Example 1  . . . . . . . . . . . . . . . . . . . . . . 10
       2.9.2.  Example 2  . . . . . . . . . . . . . . . . . . . . . . 10
       2.9.3.  Example 3  . . . . . . . . . . . . . . . . . . . . . . 11
       2.9.4.  Example 4  . . . . . . . . . . . . . . . . . . . . . . 11
       2.9.5.  Example 5  . . . . . . . . . . . . . . . . . . . . . . 11
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
     4.1.  Registration of Sieve Extension  . . . . . . . . . . . . . 14
     4.2.  Registration of ManageSieve Capability . . . . . . . . . . 14
     4.3.  Creation of Sieve URN Parameters Registry  . . . . . . . . 15
     4.4.  Registration of the "addrbook" URN parameter . . . . . . . 16
     4.5.  Registration of "sieve" URN sub-namespace  . . . . . . . . 16
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 17

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RFC 6134        Sieve Extension: Externally Stored Lists       July 2011

1.  Introduction

   This document specifies an extension to the Sieve language [RFC5228]
   for checking membership in an external list or for redirecting
   messages to an external list of recipients.  An "external list" is a