Sieve Working Group                                             B. Leiba
Internet-Draft                           IBM T.J. Watson Research Center
Intended status: Standards Track                               M. Haardt
Expires: January 9, April 7, 2008                                        freenet AG
                                                            July 8,
                                                         October 5, 2007

                  Sieve Notification Mechanism: mailto
                   draft-ietf-sieve-notify-mailto-04
                   draft-ietf-sieve-notify-mailto-05

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes a profile of the Sieve extension for
   notifications, to allow notifications to be sent by electronic mail.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.2.  Conventions used in this document  . . . . . . . . . . . . .  3

   2.    Definition . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.1.  Notify parameter "method"  . . . . . . . . . . . . . . . . .  4
   2.2.  Test notify_method_capability  . . . . . . . . . . . . . . .  4
   2.3.  Notify tag ":from" . . . . . . . . . . . . . . . . . . . . .  4
   2.4.  Notify tag ":importance" . . . . . . . . . . . . . . . . . .  4
   2.5.  Notify tag ":options"  . . . . . . . . . . . . . . . . . . .  4
   2.6.  Notify tag ":message"  . . . . . . . . . . . . . . . . . . .  4
   2.7.  Other Definitions  . . . . . . . . . . . . . . . . . . . . .  5

   3.    Examples . . . . . . . . . . . . . . . . . . . . . . . . . .  7

   4.    Internationalization Considerations  . . . . . . . . . . . .  9

   5.    Security Considerations  . . . . . . . . . . . . . . . . . . 10

   6.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . 11
   6.1.  Registration of notification mechanism . . . . . . . . . . . 11
   6.2.  New registry for Auto-Submitted header field keywords  . . . 11
   6.3.  Initial registration of Auto-Submitted header field
         keywords . . . . . . . . . . . . . . . . . . . . . . . . . . 11

   7.    References . . . . . . . . . . . . . . . . . . . . . . . . . 12 13
   7.1.  Normative References . . . . . . . . . . . . . . . . . . . . 12 13
   7.2.  Non-Normative References . . . . . . . . . . . . . . . . . . 12 13

         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 13 14
         Intellectual Property and Copyright Statements . . . . . . . 14 15

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 [mailto] URIs
   are used to generate notifications by e-mail.

1.2.  Conventions used in this document

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

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

2.  Definition

   The mailto mechanism results in the sending of a new email message (a
   "notification message") to notify a recipient about a "triggering
   message".

2.1.  Notify parameter "method"

   The mailto notification mechanism uses standard mailto URIs as
   specified in [mailto].

2.2.  Test notify_method_capability

   The notify_method_capability test for "online" may return "yes" or
   "no" only if the Sieve processor can determine with certainty whether
   or not the recipients of the notification message are online and
   logged in.  Otherwise, the test returns "maybe" for this notification
   method.

2.3.  Notify tag ":from"

   The :from tag overrides the default sender of the notification
   message.  "Sender", here, refers to the value used in the [RFC2822]
   "From" header.  Implementations MAY also use this value in the
   [RFC2821] "MAIL FROM" command (the "envelope sender"), or they may
   prefer to establish a mailbox that receives bounces from notification
   messages.

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.
   Implementations MAY use the value of :importance to set a priority or
   importance indication on the notification message (perhaps a visual
   indication, or perhaps making use of one of the non-standard but
   commonly used message headers).

2.5.  Notify tag ":options"

   This tag is not used by the mailto method.

2.6.  Notify tag ":message"

   The value of this tag, if it is present, is used as the subject of
   the notification message, and overrides all other mechanisms for
   determining the subject (as described below).  Its value SHOULD NOT
   normally be truncated, though it may be sensible to truncate an
   excessively long value.

2.7.  Other Definitions

   Because the receipt of an email message is generating another email
   message, implementations MUST take steps to avoid mail loops.  The
   notification message contains the "Received:" fields from the
   triggering message to allow loop detection as described in [RFC2821],
   section 6.2.  The implementation REQUIRED inclusion of an "Auto-Submitted:" field,
   as described in the message composition guidelines, will also help in
   loop detection and avoidance.

   Implementations MUST NOT trigger notifications for messages
   containing "Auto-Submitted:" header fields.

   Implementations MUST allow messages with empty envelope senders to
   trigger notifications.

   Because this notification method uses a store-and-forward system for
   delivery of the notification message, the Sieve processor should not
   have a need to retry notifications.  Therefore, implementations of
   this method SHOULD use normal mechanisms for submitting SMTP messages
   and for retrying the initial submission.  Once the notification
   message is submitted, implementations MUST NOT resubmit it, as this
   is likely to result in multiple notifications, and increases the
   danger of message loops.

   The overall notification message is composed using the following
   guidelines (see [RFC2822] for references to message header fields):

   o  The header field "Auto-Submitted: sieve-notify" MUST be included
      in the notification message (see [RFC3834]).  This is to reduce
      the likelihood of message loops, by tagging this as an
      automatically generated message.  Among other results, it will
      cause the notification message not to generate further
      notifications.

   o  Unless overridden by ":from", the "From:" header field and the
      envelope sender of the notification message are set either to the
      envelope "to" field from the triggering message, as used by Sieve,
      or to a fixed address (so it "comes from the notification
      system"), at the discretion of the implementation.  This may not
      be overridden by a "from" URI header, and any such URI header will
      be ignored.

   o  The "To:" header field and the envelope recipient(s) of the
      notification message are set to the address(es) specified in the
      URI (including any URI headers where the hname is "to").

   o  The "Subject:" field of the notification message contains the
      value defined by the :message notify tag, as described in
      [Notify].  If there is no :message tag and there is a "subject"
      header on the URI, then that value is used.  If that is also
      absent, the subject is retained from the triggering message.  Note
      that Sieve [Variables] can be used to advantage here, as shown in
      the example in Section 3.

   o  If the mailto URI contains a "body" header, the value of that
      header is used as the body of the notification message.  If there
      is no "body" header, it is up to the implementation whether to
      leave the body empty or to use an excerpt of the original message.

   o  The "Received:" fields from the triggering message are retained in
      the notification message, as these may help detect and prevent
      mail loops.  URI headers with hname "received" are considered
      unsafe, and will be ignored.

   o  Other header fields of the notification message that are normally
      related to an individual new message (such as "Message-ID" and
      "Date") are generated for the notification message in the normal
      manner.  Any URI headers with those names are ignored.  Further,
      the "Date" header serves as the notification timestamp defined in
      [Notify].

   o  All other header fields of the notification message either are as
      specified by URI headers, or have implementation-specific values;
      their values are not defined here.  It is suggested that the
      implementation capitalizes the first letter of URI headers and
      adds a space character after the colon between the mail header
      name and value when adding URI headers to the message.

3.  Examples

   Triggering message (received by recipient@example.org):

      Return-Path: <knitting-bounces@example.com>
      Received: from mail.example.com by mail.example.org
        for <recipient@example.org>; Wed, 7 Dec 2005 05:08:02 -0500
      Received: from hobbies.example.com by mail.example.com
        for <knitting@example.com>; Wed, 7 Dec 2005 02:00:26 -0800
      Message-ID: <1234567.89ABCDEF@example.com>
      Date: Wed, 07 Dec 2005 10:59:19 +0100
      Precedence: list
      List-Id: Knitting Mailing List <knitting.example.com>
      Sender: knitting-bounces@example.com
      Errors-To: knitting-bounces@example.com
      From: "Jeff Smith" <jeff@hobbies.example.com>
      To: "Knitting Mailing List" <knitting@example.com>
      Subject: [Knitting] A new sweater

      I just finished a great new sweater!

   Sieve script (run on behalf of recipient@example.org):

      require ["notify", "variables"];

      if header :contains "list-id" "knitting.example.com" {
        if header :matches "Subject" "[*] *" {
          notify :message "From ${1} list: ${2}"
                 :importance "3"
                 "mailto:0123456789@sms.example.net";
        }
      }

   Notification message:

      Received: from mail.example.com by mail.example.org
        for <recipient@example.org>; Wed, 7 Dec 2005 05:08:02 -0500
      Received: from hobbies.example.com by mail.example.com
        for <knitting@example.com>; Wed, 7 Dec 2005 02:00:26 -0800
      Date: Wed, 7 Dec 2005 05:08:55 -0500
      Message-ID: <A2299BB.FF7788@example.org>
      Auto-Submitted: sieve-notify
      From: <recipient@example.org>
      To: <0123456789@sms.example.net>
      Subject: From Knitting list: A new sweater
   Note that:

   o  Fields such as "Message-ID:" and "Date:" were generated afresh for
      the notification message, and do not relate to the triggering
      message.

   o  Additional "Received:" fields will be added to the notification
      message in transit; the ones shown were copied from the triggering
      message.

   o  If this message should appear at the mail.example.org server
      again, the server can use the presence of a "mail.example.org"
      received line to recognize that.  The Auto-Submitted header field
      is also present to tell the server to avoid sending another
      notification.

4.  Internationalization Considerations

   This specification introduces no specific internationalization issues
   that are not already addressed in [Sieve] and in [Notify].

5.  Security Considerations

   Sending a notification is comparable with 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.

   The automated sending of email messages exposes the system to mail
   loops, which can cause operational problems.  Implementations of this
   specification MUST protect themselves against mail loops (see
   Section 2.7).

   Additional security considerations are discussed in [Sieve] and in
   [Notify].

6.  IANA Considerations

6.1.  Registration of notification mechanism

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

   To: iana@iana.org
   Subject: Registration of new Sieve notification mechanism
   Mechanism name: mailto
   Mechanism URI: RFC2368
   Mechanism-specific tags: none
   Standards Track/IESG-approved experimental RFC number: this RFC
   Person and email address to contact for further information:
       Michael Haardt <michael.haardt@freenet-ag.de> <michael.haardt@freenet.ag>

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

6.2.  New registry for Auto-Submitted header field keywords

   Because [RFC3834] does not define a registry for new keywords used in
   the Auto-Submitted header field, we define one here, to be created as
   http://www.iana.org/assignments/auto-submitted-keywords.  This
   defines the template to be used to register new keywords.

   To: iana@iana.org
   Subject: Registration of new auto-submitted header field keyword
   Keyword value: [the text value of the field]
   Description: [a brief explanation of the purpose of this value]
   Standards Track/IESG-approved experimental RFC number: [identifies
   the specification that defines the value being registered]
   Contact: [name and email address to contact for further information]

6.3.  Initial registration of Auto-Submitted header field keywords

   The following are the initial keywords to be registered for the Auto-
   Submitted header field, to be entered in
   http://www.iana.org/assignments/auto-submitted-keywords.

   Keyword value: no
   Description: Indicates that a message was NOT automatically
   generated, but was created by a human.  It is the equivalent to the
   absence of an Auto-Submitted header altogether.
   Standards Track/IESG-approved experimental RFC number: RFC3834
   Contact: Keith Moore <moore@cs.utk.edu>
   Keyword value: auto-generated
   Description: Indicates that a message was generated by an automatic
   process, and is not a direct response to another message.
   Standards Track/IESG-approved experimental RFC number: RFC3834
   Contact: Keith Moore <moore@cs.utk.edu>

   Keyword value: auto-replied
   Description: Indicates that a message was automatically generated as
   a direct response to another message.
   Standards Track/IESG-approved experimental RFC number: RFC3834
   Contact: Keith Moore <moore@cs.utk.edu>

   Keyword value: sieve-notify
   Description: Indicates that a message was generated by a Sieve
   notification system.
   Standards Track/IESG-approved experimental RFC number: this RFC
   Contact: Michael Haardt <michael.haardt@freenet.ag>

7.  References

7.1.  Normative References

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

   [Notify]   Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
              Martin, "Sieve Extension: Notifications", work in
              progress, draft-ietf-sieve-notify, December 2005.

   [RFC2822]  Resnick, P., Ed., "Internet Message Format", RFC 2822,
              April 2001.

   [RFC3834]  Moore, K., "Recommendations for Automatic Responses to
              Electronic Mail", RFC 3834, August 2004.

   [Sieve]    Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
              Filtering Language", work in
              progress, draft-ietf-sieve-3028bis, November 2005.

   [mailto]   Hoffman, P., Masinter, L., and J. Zawinski, "The mailto
              URL scheme", RFC 2368, July 1998.

7.2.  Non-Normative References

   [RFC2821]  Klensin, J., Ed., "Simple Mail Transfer Protocol",
              RFC 2821, April 2001.

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

Authors' Addresses

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

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

   Michael Haardt
   freenet AG
   Willstaetter Str. 13
   Duesseldorf, NRW  40549
   Germany

   Phone: +49 241 53087 520
   Email: michael.haardt@freenet.ag

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