Sieve Working Group B. Leiba
Internet-Draft IBM T.J. Watson Research Center
Intended status: Standards Track M. Haardt
Expires: April 7, 2008 freenet AG
October 5, 2007
Sieve Notification Mechanism: mailto
draft-ietf-sieve-notify-mailto-05
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Copyright (C) The IETF Trust (2007).
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . . . 13
7.2. Non-Normative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . 15
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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].
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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.
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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 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").
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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.
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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
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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.
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4. Internationalization Considerations
This specification introduces no specific internationalization issues
that are not already addressed in [Sieve] and in [Notify].
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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].
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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>
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>
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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>
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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.
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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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