Sieve Working Group                                       P. Saint-Andre
Internet-Draft                                 XMPP Standards Foundation
Intended status: Standards Track                             A. Melnikov
Expires: April 3, May 10, 2008                                      Isode Limited
                                                         October 1,
                                                        November 7, 2007

                   Sieve Notification Mechanism: xmpp

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Copyright Notice

   Copyright (C) The IETF Trust (2007).


   This document describes a profile of the Sieve extension for
   notifications, to allow notifications to be sent over the Extensible
   Messaging and Presence Protocol (XMPP), also known as Jabber.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Definition . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Notify parameter "method"  . . . . . . . . . . . . . . . .  3  4
     2.2.  Notify tag ":from" . . . . . . . . . . . . . . . . . . . .  4
     2.3.  Notify tag ":options"  . . . . . . . . . . . . . . . . . .  4
     2.4.  Notify tag ":importance" . . . . . . . . . . . . . . . . .  4
     2.5.  Notify tag ":message"  . . . . . . . . . . . . . . . . . .  4
   3.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  4  5
   4.  Requirements Conformance . . . . . . . . . . . . . . . . . . .  5  6
   5.  Internationalization Considerations  . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7  8
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  7  8
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  8  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9
   Intellectual Property and Copyright Statements . . . . . . . . . . 10 11

1.  Introduction

1.1.  Overview

   The [NOTIFY] extension to the [SIEVE] mail filtering language is a
   framework for providing notifications by employing URIs to specify
   the notification mechanism.  This document defines how xmpp URIs (see
   [XMPP-URI]) are used to generate notifications via the Extensible
   Messaging and Presence Protocol (see [XMPP]), which is widely
   implemented in Jabber instant messaging technologies.

1.2.  Terminology

   This document inherits terminology from [NOTIFY], [SIEVE], and

   The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
   interpreted as described in [TERMS].

2.  Definition

   The xmpp mechanism results in the sending of an XMPP message to
   notify a recipient about an email message.  The general XMPP syntax
   is as follows:

   o  The notification MUST be an XMPP <message/> stanza.
   o  The value of the XMPP 'type' attribute MUST be 'headline' or
   o  The value of the XMPP 'from' attribute MUST be the XMPP address of
      the notification service. service associated with the SIEVE engine.
   o  The XMPP <message/> stanza MAY include a <subject/> child element
      whose value is some configurable text indicating that the message
      is a Sieve notification.
   o  The notification SHOULD include a URL URI for the recipient to use as
      a hint in locating the message, encapsulated as the XML character
      data of a <url/> child element of an <x/> element qualified by the
      'jabber:x:oob' namespace as specified in [OOB].  If included, the
      URI SHOULD be an Internet Message Access Protocol [IMAP] URL that
      specifies the location of the message as defined in [IMAP-URL],
      but MAY be another URI type that can specify or hint at the
      location of an email message, such as a URI for an HTTP resource
      [HTTP] or a POP3 mailbox [POP-URL] at which the message can be
      accessed.  It is not expected that an XMPP user agent shall
      directly handle such a URI, but instead that it shall invoke an
      appropriate helper application to handle the URI.

   The recommended mapping of the Sieve notify action into XMPP syntax
   is described in the following sections.

2.1.  Notify parameter "method"

   The "method" parameter MUST be a URI that conforms to the xmpp URI
   scheme (as specified in [XMPP-URI]) and that identifies an XMPP
   account associated with the email inbox.  The URI MAY include the
   resource identifier portion of an XMPP address but SHOULD NOT include
   an authority component, query component, or fragment identifier
   component.  The processing application MUST extract an XMPP address
   from the URI in accordance with the processing rules specified in
   [XMPP-URI].  The resulting XMPP address MUST be encapsulated in XMPP
   syntax as the value of the XMPP 'to' attribute.

2.2.  Notify tag ":from"

   The ":from" tag has no special meaning for this notification
   mechanism, and this specification puts no restriction on its use.  As
   noted, the value of the XMPP 'from' attribute specified in the XMPP
   notification message MUST be the XMPP address of the notification
   service itself. associated with the SIEVE engine.  The value of the ":from"
   tag MAY be transformed into XMPP syntax; if so, it SHOULD be
   encapsulated as the value of an XMPP [SHIM] header named "Reply-To".

2.3.  Notify tag ":options"

   The ":options" tag has no special meaning for this notification
   mechanism.  Any handling of this tag is the responsibility of an

2.4.  Notify tag ":importance"

   The ":importance" tag has no special meaning for this notification
   mechanism, and this specification puts no restriction on its use.
   The value of the ":importance" tag MAY be transformed into XMPP
   syntax (in addition to or instead of including in the default
   message); if so, it MUST SHOULD be encapsulated as the value of an XMPP
   [SHIM] header named "Urgency", and where the XML character of that header
   MUST be
   is "high" if the value of the ":importance" tag is "1", "medium" if
   the value of the ":importance" tag is "2", or and "low" if the value of
   the ":importance" tag is "3".

2.5.  Notify tag ":message"

   If included, the ":message" tag is included, that string MUST be transformed
   into the XML character data of an XMPP <body/> element. element (where the
   string is generated according to the guidelines specified in Section
   3.6 of [NOTIFY]).  If the ":message" tag is not included, the rule
   specified in [NOTIFY] SHOULD be followed, as shown in the examples
   below. followed.

3.  Examples

   In the following examples, the sender of the email has an address of
   <>, the entity to be notified has an XMPP
   address of (resulting in an XMPP URI of
   <>), and the notification service associated
   with the SIEVE engine has an XMPP address of
   (resulting in an XMPP URI of <xmpp:>). <>).

   The following is a basic Sieve notify action with only a method:

     notify ""

   The resulting XMPP <message/> stanza might be as follows:

     <message from=''
       <subject>A Sieve instant notification!</subject>
       <body>&lt;; Wherefore art thou?</body>
       <subject>Sieve notification</subject>
       <body>&lt;; You have new mail.</body>

   The following is a more advanced Sieve notify action with a method,
   importance, subject, and message, as well as a URL pointing to the

     notify :importance "1"
            :message "Contact Juliet immediately!"

   The resulting XMPP <message/> stanza might be as follows:

     <message from=''
       <subject>Sieve notification</subject>
       <body>Contact Juliet immediately!</body>
       <headers xmlns=''>
         <header name='Urgency'>high</header>
       <x xmlns='jabber:x:oob'>

4.  Requirements Conformance

   Section 3.8 of [NOTIFY] specifies a set of requirements for Sieve
   notification methods.  The conformance of the xmpp notification
   mechanism is provided here.

   1.  An implementation of the xmpp notification method SHOULD NOT
       modify the final notification text (e.g., to limit the length);
       however, a given deployment MAY do so (e.g., if recipients pay
       per character or byte for XMPP messages).  Modification of
       characters themselves should not be necessary, since XMPP
       character data is encoded in [UTF-8].
   2.  An implementation MAY ignore parameters specified in the ":from",
       ":importance", and ":options" tags.
   3.  There is no recommended default message for an implementation to
       include if the ":message" argument is not specified.
   4.  A notification sent via the xmpp notification method MAY include
       a timestamp in the textual message.
   5.  The value of the XMPP 'from' attribute MUST be the XMPP address
       of the xmpp notification service. service associated with the SIEVE
       engine.  The value of the Sieve ":from" tag MAY be transformed
       into the value of an XMPP [SHIM] header named "Reply-To".
   6.  An implementation MUST NOT include any other extraneous
       information not specified in parameters to the notify action.
   7.  In accordance with [XMPP-URI], an implementation MUST ignore any
       URI action or parameter it does not understand (i.e., the URI
       MUST be processed as if the action or parameter were not
       present).  It is RECOMMENDED to support the XMPP "message" query
       type (see [QUERIES]) and the associated "body" and "subject"
       parameters, which parameters SHOULD be mapped to the XMPP <body/>
       and <subject/> child elements of the XMPP <message/> stanza type,
       respectively.  However, if included then the Sieve notify
       ":message" parameter MUST be mapped to the XMPP <body/> element,
       overriding the "body" parameter (if any) included in the XMPP
   8.  In response to a notify_method_capability test for the "online"
       notification-capability, an implementation SHOULD return a value
       of "yes" if it has knowledge of an active presence session for
       the specified notification-uri and a value of "no" if it does not
       have such knowledge.
   9.  An implementation SHOULD NOT attempt to retry delivery of a
       notification if it receives an XMPP error of type "auth" or
       "cancel", MAY attempt to retry delivery if it receives an XMPP
       error of type "wait", and MAY attempt to retry delivery if it
       receives an XMPP error of "modify" but only if it makes
       appropriate modifications to the notification (see [XMPP]); in
       any case the number of retries SHOULD be limited to a
       configurable number no less than 3 and no more than 10.  An
       implementation MAY throttle notifications if the number of
       notifications within a given time period becomes excessive
       according to local service policy.  Duplicate suppression (if
       any) is a matter of implementation and is not specified herein.

5.  Internationalization Considerations

   Although an XMPP address may contain nearly any [UNICODE] character,
   the value of the "method" parameter MUST be a Uniform Resource
   Identifier (see [URI]) rather than an Internationalized Resource
   Identifier (see [IRI]).  The rules specified in [XMPP-URI] MUST be
   followed when generating XMPP URIs.

   In accordance with Section 13 of RFC 3920, all data sent over XMPP
   MUST be encoded in [UTF-8].

6.  Security Considerations

   Depending on the information included, sending a notification can be
   comparable to forwarding mail to the notification recipient.  Care
   must be taken when forwarding mail automatically, to ensure that
   confidential information is not sent into an insecure environment.
   In particular, implementations MUST conform to the security
   considerations given in [NOTIFY], [SIEVE], and [XMPP].

7.  IANA Considerations

   The following template provides the IANA registration of the Sieve
   notification mechanism specified in this document:

     Subject: Registration of new Sieve notification mechanism
     Mechanism name: xmpp
     Mechanism URI: RFC4622
     Mechanism-specific tags: none
     Standards Track/IESG-approved experimental RFC number: this RFC
     Person and email address to contact for further information:
          Peter Saint-Andre <>

   This information should be added to the list of Sieve notification
   mechanisms maintained at

8.  References

8.1.  Normative References

   [NOTIFY]   Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
              "Sieve Extension: Notifications",
              draft-ietf-sieve-notify-08 (work in progress), July 2007.

   [OOB]      Saint-Andre, P., "Out of Band Data", XSF XEP 0066,
              August 2006.

   [QUERIES]  Saint-Andre, P., "XMPP URI Scheme Query Components", XSF
              XEP 0147, September 2006.

   [SHIM]     Saint-Andre, P. and J. Hildebrand, "Stanza Headers and
              Internet Metadata", XSF XEP 0131, August 2005.

   [SIEVE]    Showalter, T. and P. Guenther, "Sieve: An Email Filtering
              Language", draft-ietf-sieve-3028bis-12 draft-ietf-sieve-3028bis-13 (work in progress),
              October 2007.

   [TERMS]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

              Saint-Andre, P., "Internationalized Resource Identifiers
              (IRIs) and Uniform Resource Identifiers (URIs) for the
              Extensible Messaging and Presence Protocol (XMPP)",
              draft-saintandre-rfc4622bis-01 (work in progress),
              June 2007.

8.2.  Informative References

   [HTTP]     Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

              4rev1", RFC 3501, March 2003.

              Newman, C. and A. Melnikov, "IMAP URL Scheme",
              draft-ietf-lemonade-rfc2192bis-09 (work in progress),
              August 2007.

   [POP-URL]  Gellens, R., "POP URL Scheme", RFC 2384, August 1998.

   [IRI]      Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard, Version
              3.2.0", 2000.

              The Unicode Standard, Version 3.2.0 is defined by The
              Unicode Standard, Version 3.0 (Reading, MA, Addison-
              Wesley, 2000.  ISBN 0-201-61633-5), as amended by the
              Unicode Standard Annex #27: Unicode 3.1
              ( and by the Unicode
              Standard Annex #28: Unicode 3.2

   [URI]      Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [UTF-8]    Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [XMPP]     Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

Authors' Addresses

   Peter Saint-Andre
   XMPP Standards Foundation


   Alexey Melnikov
   Isode Limited


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