Sieve Working Group                                             B. Leiba
Internet-Draft                           IBM T.J. Watson Research Center
Expires: June 10, 2006 April 19, 2007                                        M. Haardt
                                                           freenet.de AG
                                                        December 7, 2005
                                                        October 16, 2006

                  Sieve Notification Mechanism: mailto
                   draft-ietf-sieve-notify-mailto-00
                   draft-ietf-sieve-notify-mailto-01

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Copyright Notice

   Copyright (C) The Internet Society (2005). (2006).

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

   2.    Definition . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.1
   2.1.  Notify tag ":method" . . . . . . . . . . . . . . . . . . . . .  4
   2.2 Notify tag ":id" . . . . . . . . . . . . . . . . . . . . . . .  4
   2.3
   2.2.  Notify tag ":priority" . . . . . . . . . . . . . . . . . . . .  4
   2.4
   2.3.  Notify tag ":message"  . . . . . . . . . . . . . . . . . . . .  4
   2.5
   2.4.  Other Definitions  . . . . . . . . . . . . . . . . . . . . . .  5

   3.    Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  6  7

   4.    Internationalization Considerations  . . . . . . . . . . . . .  8  9

   5.    Security Considerations  . . . . . . . . . . . . . . . . . . .  9 10

   6.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10 11

   7.    References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
   7.1 12
   7.1.  Normative References . . . . . . . . . . . . . . . . . . . . . 11
   7.2 12
   7.2.  Non-Normative References . . . . . . . . . . . . . . . . . . . 11 12

         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11 13
         Intellectual Property and Copyright Statements . . . . . . . . 13 14

1.  Introduction

1.1

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

1.2.  Conventions used in this document

   Conventions for notations are as in [Sieve] section 1.1, including
   the use of [Kwds] and the use of [ABNF].
   [[no abnf ref: We don't actually need the ABNF reference...]]

   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

2.1.  Notify tag ":method"

   The mailto notification mechanism uses standard mailto URIs as
   specified in [mailto].  URI parameters headers with hname "from", "subject" and
   "received" are ignored if specified; all other parameters URI headers are
   accepted.

   [[Barry ignored: Should we ignore them, or should their presence be
   an error?]]

2.2  Notify tag ":id"

   [[Michael ignored: The :id tag has no special meaning mailto URI spec allows for this notification mechanism,
   and this specification puts no restriction on its use.

2.3 either.  I like
   ignoring them more, because it fits into the picture of ignoring a
   different sender for other message-generating actions, if it is
   forbidden.]]

2.2.  Notify tag ":priority"

   The :priority tag has no special meaning for this notification
   mechanism, and this specification puts no restriction on its use.
   Implementations MAY use the value of :priority to set a priority or
   importance indication on the notification message.

2.4

2.3.  Notify tag ":message"

   o  The  Unless overridden by ":from", the "From:" header field and the
      envelope sender of the notification message are set to the
      envelope "to" field from the triggering message, as used by Sieve.

      [[Barry from: It might be better in some cases for the
      notification to "come from" the sender of the triggering message.
      In other cases it might be better for all notifications to come
      from the "mail system".  I think we should define a way to specify
      the behaviour here, perhaps with a new notify tag.]]

      [[Michael from: Variables could perform both.  Does that
      suffice?]]

      [[Barry sender: Should we also provide a mapping or setting for
      the "Sender:" header field?]]

      [[Michael sender: If that is required, the base spec should allow
      it for all methods, like it offers ":from".]]
   o  The "To:" header field and the envelope recipient(s) of the
      notification message are set to the address(es) specified in URI
      (including any URI parameters headers where the hname is "to").

      [[Barry to: I'd like some way to specify that the To: header
      should be retained from the triggering message.  In fact, I'd like
      a way to say that ALL headers be retained.]]

      [[Michael to: Retaining the original "To:" field could easily
      result in a loop.  I think we need to define the focus of this
      method: Generic SMTP message generation, or "just notifications"
      over SMTP?]]

   o  The "Received:" headers field from the triggering message are retained in
      the notification message, as these may help detect and prevent
      mail loops.

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

   o  All other header fields of the notification message either are as
      specified in the URI, 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.

   o  If the mailto URI contains a "body" parameter, header, the value of that
      parameter
      header is used as the body of the notification message.  If there
      is no "body" parameter, header, the body of the notification message is
      empty.

      [[Barry body: I'd like some way to specify that the body contain
      the body of the triggering message.]]

2.5

      [[Michael body: Can variables do that?  I don't know.]]

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

   [[Barry loops: We should say more about this...]]

   [[Michael loops: Ok now?  Informal reference or normative?  Could you
   add it?]]

   [[comment 1: Mailto URIs focus on the message, not its submission.
   There is no way to specify envelope parameters, require encryption or
   authentication.  Sure enough there is more than SMTP, so mailto is
   fine not to address this specific transport, but should we ever need
   more, it can not be specified as URI parameter, header, because there is no room
   in its namespace.]]

   [[comment 2: Michael tried to get documentation on SMTP-SMS gateways,
   but everybody operating one keeps the specification like a precious
   secret.  From experiments made some years ago, we know some gateways
   ignore all messages with empty envelope senders, some do not
   implement MIME and some ignore the body.  Using empty envelope
   senders to avoid loops is not possible and it would not allow to send
   notifications about bounces.]] body.]]

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 :method "mailto:0123456789@sms.example.net"
                 :message "From ${1} list: ${2}"
                 :priority "3";
        }
      }

   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>
      From: <recipient@example.org>
      To: <0123456789@sms.example.net>
      Subject: From Knitting list: A new sweater
   Note that:

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

   o  Additional "Received:" headers 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 avoid sending another notification.

4.  Internationalization Considerations

   [[Internationalization: What do we say here?]]

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.

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

6.  IANA Considerations

   [[IANA to-do: What do we need to do to actually get this set up with
   IANA?]]
   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: draft-duerst-mailto-bis (change to RFC----)
   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@freenet-ag.de> <michael.haardt@freenet-ag.de>

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

7.  References

7.1

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.

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

   [mailto]  Duerst, M., Masinter, L., and J. Zawinski, "The mailto URI
             scheme", work in progress, draft-duerst-mailto-bis,
             February 2005.

7.2

7.2.  Non-Normative References

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

   [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.de AG
   Willstaetter Str. 13
   Duesseldorf, NRW  40549
   Germany

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

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