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Versions: (draft-martin-sieve-notify) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5435

Sieve Working Group                                     A. Melnikov, Ed.
Internet-Draft                                             Isode Limited
Intended status: Standards Track                           B. Leiba, Ed.
Expires: August 24, 2007                                    W. Segmuller
                                         IBM T.J. Watson Research Center
                                                               T. Martin
                                                    BeThereBeSquare Inc.
                                                       February 20, 2007

                     Sieve Extension: Notifications

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   The list of current Internet-Drafts can be accessed at

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   This Internet-Draft will expire on August 24, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).


   Users go to great lengths to be notified as quickly as possible that
   they have received new mail.  Most of these methods involve polling
   to check for new messages periodically.  A push method handled by the
   final delivery agent gives users quicker notifications and saves

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   server resources.  This document does not specify the notification
   method but it is expected that using existing instant messaging
   infrastructure such as XMPP, or SMS messages will be popular.  This
   draft describes an extension to the Sieve mail filtering language
   that allows users to give specific rules for how and when
   notifications should be sent.

Changes since draft-ietf-sieve-notify-06

   o  Remove extract_text.  The WG consensus was to move it to another
      document, such as Sieve MIME loops.

   o  Deleted markers for open issues from the document.

   o  Clarified that a notification mechanism can treat some URI
      parameters as an error.

   o  Added notify_method_capability test and example.

   o  Minor corrections to the IANA registration as a result of other

Changes since draft-ietf-sieve-notify-05

   o  Fixed XMPP URI in one example.

   o  Addressed Michael's issue with how timestamp are described.

   o  Renamed "valid_notif_method" to "valid_notify_method".

   o  Added text about truncation of a textual part when it is stored in
      a variable using extract_text.

   o  Changed tagged :method argument to positional argument.

   o  Added text about notification throttling, identifying notification
      source and restricting values of the :from parameter.

   o  Added a requirement on documents describing notification methods
      to list which URI parameters must be ignored.

Changes since draft-ietf-sieve-notify-04

   o  Made notification method required.

   o  Defined "mailto" as a mandatory-to-implement method.

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   o  Added normative reference to mailto.

   o  Clarified that :importance may be treated as a transport

   o  Clarified that :importance value can be included in the default
      :message, if one is not specified.

   o  Made the default :message implementation specific.

   o  Renamed the capability name from "notify" to "enotify"

   o  Updated IANA registration.

   o  Moved text about ManageSieve capability to the ManageSieve
      document itself.

   o  Removed reference to IANA registry for options.

   o  Some miscellaneous text cleanup and clarification.

Changes since draft-ietf-sieve-notify-03

   o  Added a warning that "notify" must not be used as a crappy form of

   o  Added a warning about using "notify" to forward confidential
      information in order to bypass organization's policy.

   o  Fixed syntax of the :options argument - it is a string list, each
      string containing "<attribute>=<value>"

   o  Renamed :priority to :importance

   o  Cleaned up section about requirements on methods.

Changes since draft-ietf-sieve-notify-02

   o  Added :from tagged argument.

   o  Added Extract_text action, which allows to extract content of the
      first text/* part.

   o  Added back the ":options" parameter to the notify action.

   o  Added new section talking about requirements on notification
      method specs.

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   o  Added more examples.

Changes since draft-ietf-sieve-notify-00

   o  Updated references, etc.

   o  Added IANA considerations section.

   o  Removed denotify action.

   o  Updated examples to use the variables extension.

   o  Replaced notification method with URI.

   o  Removed text suggesting that this extension can be used to track
      all Sieve actions taken.

   o  Changed priority to be a string.

   o  Added text about URI verification.

   o  Clarified that a notification method is allowed to perform
      adaptation of notification context (e.g. truncation, charset
      conversion, etc.).  These adaptations must be documented in a
      document describing the notification method.

   o  Clarified that notify is compatible with all existing actions.

   o  Removed the :id parameter to the notify action.

   o  Added valid_notif_method test that allows to test if an
      notification method (URI) is supported.

   o  Added a new capability response to ManageSieve that allows to
      report supported notification types.

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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  6
   1.1.  Conventions used in this document  . . . . . . . . . . . . .  6

   2.    Capability Identifier  . . . . . . . . . . . . . . . . . . .  6

   3.    Notify Action  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.1.  Notify Action Syntax and Semantics . . . . . . . . . . . . .  6
   3.2.  Notify parameter "method"  . . . . . . . . . . . . . . . . .  6
   3.3.  Notify tag ":from" . . . . . . . . . . . . . . . . . . . . .  7
   3.4.  Notify tag ":importance" . . . . . . . . . . . . . . . . . .  7
   3.5.  Notify tag ":options"  . . . . . . . . . . . . . . . . . . .  8
   3.6.  Notify tag ":message"  . . . . . . . . . . . . . . . . . . .  8
   3.7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   3.8.  Requirements on notification methods specifications  . . . . 11

   4.    Test valid_notify_method . . . . . . . . . . . . . . . . . . 12

   5.    Test notify_method_capability  . . . . . . . . . . . . . . . 13

   6.    Interactions with Other Sieve Actions  . . . . . . . . . . . 14

   7.    Security Considerations  . . . . . . . . . . . . . . . . . . 14

   8.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . 15

   9.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15

   10.   References . . . . . . . . . . . . . . . . . . . . . . . . . 16
   10.1. Normative References . . . . . . . . . . . . . . . . . . . . 16
   10.2. Informative References . . . . . . . . . . . . . . . . . . . 16

         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
         Intellectual Property and Copyright Statements . . . . . . . 18

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1.  Introduction

   This is an extension to the Sieve language defined by [Sieve] for
   providing instant notifications.  It defines the new action "notify".

   This document does not specify the notification methods.  Examples of
   possible notification methods are email and XMPP.  To allow a
   mechanism for portability of scripts that use notifications,
   implementation of the [MailTo] method is mandatory.  Other available
   methods shall depend upon the implementation and configuration of the

1.1.  Conventions used in this document

   Conventions for notations are as in [Sieve] section 1.1, including
   the use of [ABNF].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [Kwds].

2.  Capability Identifier

   The capability string associated with the extension defined in this
   document is "enotify".

3.  Notify Action

3.1.  Notify Action Syntax and Semantics

   Usage:  notify [":from" string]
           [":importance" <"1" / "2" / "3">]
           [":options" string-list]
           [":message" string]
           <method: string>

   The Notify action specifies that a notification should be sent to a
   user.  The format of the notification is implementation-defined and
   is also affected by the notification method used (see Section 3.2).
   However, all content specified in the :message parameter SHOULD be

3.2.  Notify parameter "method"

   The method positional parameter identifies the notification method
   that will be used; it is a URI [URI].  For example, the notification

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   method can be an SMS URI [SMS-URI] containing a phone number, or an
   XMPP [XMPP] URI containing an XMPP identifier [XMPP-URI].

   The supported URI values will be site-specific, but support for the
   [MailTo] method is REQUIRED in order to insure interoperability.  If
   a URI schema is specified that the implementation does not support,
   the notification MUST cause an error condition.  Sieve scripts can
   check the supported methods using the "valid_notify_method" test to
   be sure that they only use supported ones, to avoid such error

   If the method parameter contains a supported URI schema, then the URI
   MUST be checked for syntactic validity.  An invalid URI syntax or an
   unsupported URI extension MUST cause an error.  An implementation MAY
   enforce other semantic restrictions on URIs -- for example an SMS URI
   can only contain phone numbers in a particular geographical region --
   and will treat violations of such semantic restrictions as errors.

3.3.  Notify tag ":from"

   A ":from" parameter may be used to specify an author of the
   notification.  The syntax of this parameter's value is method-
   specific.  Implementations SHOULD check the syntax according to the
   notification method specification and generate an error when a
   syntactically invalid ":from" parameter is specified.  In order to
   minimize/prevent forgery of the author value, implementations SHOULD
   impose restrictions on what values can specified in a ":from"
   parameter; it is suggested that values which fail such a validity
   check simply be ignored rather than causing the notify action to

3.4.  Notify tag ":importance"

   The :importance tag specifies the importance of the delivery of the
   notification.  The :importance tag is followed by a numeric value
   represented as a string: "1" (high importance), "2" (normal
   importance), and "3" (low importance).  If no importance is given,
   the default value "2" SHOULD be assumed.  A notification method can
   treat the importance value as a transport indicator.  For example, it
   might deliver notifications of high importance quicker than
   notifications of normal or low importance.  Some notification methods
   allow users to specify their state of activity (for example "busy" or
   "away from keyboard").  If the notification method provides this
   information it SHOULD be used to selectively send notifications.  If,
   for example, the user marks herself as "busy", a notification method
   can require that a notification with importance of "3" is not to be
   sent, however the user should be notified of a notification with
   higher importance.

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   If the notification method allows users to filter messages based upon
   certain parameters in the message, users SHOULD be able to filter
   based upon importance.  If the notification method does not support
   importance, then this parameter MUST be ignored, however an
   implementation MAY include the importance value in the default
   message Section 3.6, if one is not provided.

3.5.  Notify tag ":options"

   The :options tag is used to send additional parameters to the
   notification method.  Interpretation of the parameters is method-
   specific.  This document doesn't specify any such additional

   Each string in the options string list has the following syntax:

3.6.  Notify tag ":message"

   The :message tag specifies the message data to be included in the
   notification.  The entirety of the string SHOULD be sent but
   implementations MAY shorten the message for technical or aesthetic
   reasons.  If the message parameter is absent, a default
   implementation-specific message is used.  Unless specified otherwise
   by a particular notification mechanism, an implementation default
   containing at least the value of the "From" header field and the
   value of the "Subject" header field is RECOMMENDED.

   In order to construct more complex messages the notify extension can
   be used together with the Sieve variables extension [Variables], as
   shown in the examples below.

3.7.  Examples

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   Example 1:
       require ["enotify", "fileinto", "variables"];

       if header :contains "from" "boss@example.org" {
           notify :importance "1"
               :message "This is probably very important"
           # Don't send any further notifications

       if header :contains "to" "sievemailinglist@example.org" {
           # :matches is used to get the value of the Subject header
           if header :matches "Subject" "*" {
               set "subject" "${1}";

           # :matches is used to get the value of the From header
           if header :matches "From" "*" {
               set "from" "${1}";

           notify :importance "3"
               :message "[SIEVE] ${from}: ${subject}"
           fileinto "INBOX.sieve";

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   Example 2:
       require ["enotify", "fileinto", "variables", "envelope"];

       if header :matches "from" "*@*.example.org" {
           # :matches is used to get the MAIL FROM address
           if envelope :all :matches "from" "*" {
               set "env_from" " [really: ${1}]";

           # :matches is used to get the value of the Subject header
           if header :matches "Subject" "*" {
               set "subject" "${1}";

           # :matches is used to get the address from the From header
           if address :matches :all "from" "*" {
               set "from_addr" "${1}";

           notify :message "${from_addr}${env_from}: ${subject}"

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 Example 3:
     require ["enotify", "variables"];

     set "notif_method"

     if header :contains "subject" "Your dog" {
         set "notif_method" "sms:+14085551212";

     if header :contains "to" "sievemailinglist@example.org" {
         set "notif_method" "";

     if not string :is "${notif_method}" "" {
         notify "${notif_method}";

     if header :contains "from" "boss@example.org" {
         # :matches is used to get the value of the Subject header
         if header :matches "Subject" "*" {
             set "subject" "${1}";

         # don't need high importance notification for
         # a 'for your information'
         if not header :contains "subject" "FYI:" {
             notify :importance "1" :message "BOSS: ${subject}"

3.8.  Requirements on notification methods specifications

   This section describes requirements for documents that define
   specific Sieve notification methods.

   A notification method MAY allow modification of the final
   notification text -- for example, truncating it if it exceeds a
   length limit, or modifying characters that can not be represented in
   the target character set.  Characters in the notification text which
   can't be represented by the notification method SHOULD be replaced
   with a symbol indicating an unknown character.  Allowed modifications
   MUST be documented in the document describing the notification

   A notification method MAY ignore parameters specified in the Notify

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   A notification method MAY recommend the default message value to be
   used if the :message argument is not specified.

   Notifications SHOULD include timestamps, if the notification method
   allows for their transmission outside of the textual message.
   Implementation methods which can only transmit timestamps in the
   textual message MAY include them in the textual message.

   Notifications SHOULD includes means to identify/track its origin, in
   order to allow a recipient to stop notifications or find out how to
   contact the sender.  This requirement is to help tracking a
   misconfigured or abusive origin of notifications.

   Methods SHOULD NOT include any other extraneous information not
   specified in parameters to the notify action.

   Methods MUST specify which URI parameters (if any) must be ignored,
   which ones must be used in the resulting notification and which ones
   must cause an error.

   Methods MUST specify what values are returned by the
   notify_method_capability test Section 5.

   If there are errors sending the notification, the Sieve interpreter
   SHOULD ignore the notification and not retry indefinitely.  The Sieve
   interpreter MAY throttle notifications; if it does, a request to send
   a notification can be silently ignored.  Documents describing
   notification methods SHOULD describe how retries, throttling,
   duplicate suppression (if any), etc. are to be handled by

4.  Test valid_notify_method

   Usage:  valid_notify_method <notification-uris: string-list>

   The "valid_notify_method" test is true if the notification methods
   listed in the notification-uris argument are supported and they are
   syntactically (including URI parameters) and semantically (including
   implementation-specific semantic restrictions) valid.  This test MUST
   perform exactly the same validation as would be performed on the
   "method" parameter to the "notify" action.

   The test is true only if ALL of the listed notification methods are
   supported and valid.

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   Example 4 (partial):
             if not valid_notify_method ["mailto:",
                     "http://gw.example.net/notify?test"] {

5.  Test notify_method_capability

   Usage:  notify_method_capability [COMPARATOR] [MATCH-TYPE]
           <notification-uri: string>
           <notification-capability: string>
           <key-list: string-list>

   The "notify_method_capability" test retrieves the notification
   capability specified by the notification-capability string that is
   specific to the notification-uri and matches it to the values
   specified in the key-list.  The test succeeds if a match occurs.  The
   type of match defaults to ":is" and the default comparator is

   The notification-capability is case insensitive.

   The notify_method_capability test MUST fail unconditionally if the
   specified notification-uri is syntactically invalid (as determined by
   the valid_notify_method test Section 4) or specifies an unsupported
   notification method.  However this MUST NOT cause an error.

   The notify_method_capability test MUST fail unconditionally if the
   specified notification-capability item does not exist.  A script MUST
   NOT fail with an error if the item does not exist.  This allows
   scripts to be written that handle nonexistent items gracefully.

   This document defines a single notification-capability value
   "online", which is described below.  Additional notification-
   capability values may be defined by a Standard Track or Experimental

   For the "online" notification-capability the notify_method_capability
   test can match one of the following key-list values:

   o  "yes" - the entity identified by the notification-uri can receive
      a notify notification immediately.  Note that even after this
      value is returned, there is no guaranty that the entity would
      actually be able to receive any notification immediately or even
      receive it at all.  Transport errors, recipient policy, etc. can
      prevent that.

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   o  "no" - the entity identified by the notification-uri is not
      currently available to receive an immediate notification.

   o  "maybe" - Sieve interpreter can't determine if the the entity
      identified by the notification-uri is online or not.

   The "relational" extension [Relational] adds a match type called
   ":count".  The count of an notify_method_capability test is 0 if the
   returned information is the empty string, or 1 otherwise.

   Example 5:
             require ["enotify"];

             if notify_method_capability
                    "yes" {
                 notify :importance "1" :message "You got mail"
             } else {
                 notify :message "You got mail" "sms:+14085551212";

6.  Interactions with Other Sieve Actions

   The notify action is compatible with all other actions, and does not
   affect the operation of other actions.  In particular, the notify
   action MUST NOT cancel the implicit keep.

   Multiple executed notify actions are allowed.  Specific notification
   methods MAY allow multiple notifications from the same script to be
   collapsed into one.

7.  Security Considerations

   Security considerations are discussed in [Sieve].  Additionally,
   implementations must be careful to follow the security considerations
   of the specific notification methods.

   The notify action is potentially very dangerous.  The path the
   notification takes through the network may not be secure.  An error
   in the options string may cause the message to be transmitted to
   someone it was not intended for, or may expose information to

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   Just because a notification is received doesn't mean that it was sent
   by the Sieve implementation.  It might be possible to forge
   notifications with some notification methods.

   An organization may have a policy about the forwarding of classified
   information to unclassified networks.  Unless the policy is also
   enforced in the module responsible for generating (or sending) of
   notifications, users can use the extension defined in this document
   to extract classified information and bypass the policy.

   Notifications can result in loops and bounces.  In particular, a
   notification to an email address will not contain necessary Received
   header fields that might be otherwise used to prevent mail loops.
   All notification methods must take care to provide mechanisms for
   avoiding notification loops.

8.  IANA Considerations

   The following template specifies the IANA registration of the notify
   Sieve extension specified in this document:

   To: iana@iana.org
   Subject: Registration of new Sieve extension
   Capability name: enotify
   Description: adds the 'notify' action for notifying user about the
   received message.  It also provides two new test: valid_notify_method
   checks notification URIs for validity; notify_method_capability can
   check recipients capabilities.
   RFC number: this RFC
   Contact address:
       The Sieve discussion list <ietf-mta-filters@imc.org>

   This information should be added to the list of sieve extensions
   given on http://www.iana.org/assignments/sieve-extensions.

9.  Acknowledgements

   Thanks to Larry Greenfield, Sarah Robeson, Tim Showalter, Cyrus
   Daboo, Nigel Swinson, Kjetil Torgrim Homme, Michael Haardt, Mark E.
   Mallett, Ned Freed, Lisa Dusseault, Dilyan Palauzov, Arnt Gulbrandsen
   and Peter Saint-Andre for help with this document.

10.  References

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10.1.  Normative References

   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

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

   [MailTo]   Leiba, B. and M. Haardt, "Sieve Notification Mechanism:
              mailto", work in progress, draft-ietf-sieve-notify-mailto,
              October 2006.

              Segmuller, W. and B. Leiba, "Sieve Extension: Relational
              Tests", work in progress, draft-ietf-sieve-3431bis,
              December 2005.

   [Sieve]    Guenther, P. and T. Showalter, "Sieve: An Email Filtering
              Language", work in progress, draft-ietf-sieve-3028bis,
              August 2006.

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

              Homme, K., "Sieve Extension: Variables", work in
              progress, draft-ietf-sieve-variables, December 2005.

10.2.  Informative References

   [SMS-URI]  Wilde, E. and A. Vaha-Sipila, "URI scheme for GSM Short
              Message Service", work in progress, draft-wilde-sms-uri,
              August 2005.

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

              Saint-Andre, P., "Internationalized Resource Identifiers
              (IRIs) and Uniform Resource Identifiers (URIs) for the
              Extensible Messaging and Presence Protocol (XMPP)", work
              in progress, draft-saintandre-xmpp-iri, September 2005.

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Authors' Addresses

   Alexey Melnikov (editor)
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex  TW12 2BX

   Email: Alexey.Melnikov@isode.com

   Barry Leiba (editor)
   IBM T.J. Watson Research Center
   19 Skyline Drive
   Hawthorne, NY  10532

   Phone: +1 914 784 7941
   Email: leiba@watson.ibm.com

   Wolfgang Segmuller
   IBM T.J. Watson Research Center
   19 Skyline Drive
   Hawthorne, NY  10532

   Phone: +1 914 784 7408
   Email: werewolf@us.ibm.com

   Tim Martin
   BeThereBeSquare Inc.
   672 Haight st.
   San Francisco, CA  94117

   Phone: +1 510 260-4175
   Email: timmartin@alumni.cmu.edu

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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an

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   Administrative Support Activity (IASA).

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