Network Working Group N. Freed
Internet-Draft Sun Microsystems
Expires: February 1, 2009 July 31, 2008
Sieve Email Filtering: Notary Extension
draft-freed-sieve-notary-01
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Abstract
This document describes the "dsn-envelope" and "dsn-redirect"
extensions to the Sieve email filtering language. The "dsn-envelope"
extension provides access to additional envelope information provided
by the delivery status notification extension to SMTP defined in RFC
3461. The "dsn-redirect" extension extends Sieve's redirect action
to provide control over delivery status notification parameters.
Change History (to be removed prior to publication as an RFC
Fixed several typos.
Changed name of extension from notary to dsn-envelope.
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Added the dsn-redirect extension.
Updated references.
Added a note about the use of ADDRESS-PART arguments with the new
envelope-part strings defined by the dsn-envelope extension.
Fleshed out the dsn-redirect extension.
1. Introduction
Sieve [RFC5228] is a language for filtering email messages at or
around the time of final delivery. It is designed to be
implementable on either a mail client or mail server. It is suitable
for running on a mail server where users may not be allowed to
execute arbitrary programs, such as on black box Internet Message
Access Protocol [RFC3501] servers, as it has no user-controlled loops
or the ability to run external programs.
The base sieve specification defines the envelope extension and test
to access information in the message envelope. Only information
available in regular SMTP is provided; additional information added
to the SMTP envelope by SMTP extensions cannot be accessed. The
"dsn-envelope" extension extends the envelope test to allow access to
the additional envelope fields defined by the SMTP extension for
delivery status notification specified in RFC 3461 [RFC3461].
The base sieve specification also defines the redirect action which
sends the message to a different address. Redirect only allows
specification of the new recipient address. The "dsn-redirect"
extension extends redirect to allow specification of some fields
defined by the delivery status notification SMTP extension.
2. Conventions used in this document
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 BCP 14 [RFC2119].
The terms used to describe the various components of the Sieve
language are taken from Section 1.1 of [RFC5228].
This document uses the ABNF notation specified in [RFC5234] and
refers to the ABNF production notify-esmtp-value defined in Section
4.1 of [RFC3461].
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3. Capability Identifier
The capability strings associated with the extensions defined in this
document are "dsn-envelope" and "dsn-redirect".
4. Dsn-envelope extension
The "dsn-envelope" extension does not define any new tests or
actions, rather, it adds four values to the list of possible (case-
insensitive) envelope-part strings defined in Section 5.4 of
[RFC5228]:
notify Match the list of notification conditions, or NOTIFY values,
associated with TO address used in the SMTP RCPT TO command that
resulted in this message getting delivered to this user. More
than one notification condition can be in effect at once; each
condition that is in effect is tested separately and any match
causes the text to succeed. The syntax and semantics of the
NOTIFY parameter are defined in RFC 3461 [RFC3461] section 4.1.
Currently the possible notification condition values are "NEVER",
"SUCCESS", "FAILURE" and "DELAY". Note that the value "NEVER"
cannot be combined with any other value.
orcpt Match the original recipient, or ORCPT, value in decoded form
associated with the TO address used in the SMTP RCPT TO command
that resulted in this message getting delivered to this user. The
syntax and semantics of the ORCPT parameter are defined in Section
2.2 of RFC 3461 [RFC3461].
ret Match the return of content, or RET, value given in the SMTP
MAIL FROM command. The syntax and semantics of the RET parameter
are defined in RFC 3461 [RFC3461] section 4.3. Currently the
possible return of content values are "FULL" and "HDRS".
envid Match the envelope identifier, or ENVID, value in decoded form
given in the SMTP MAIL FROM command. The syntax and semantics of
the ENVID parameter are defined in Section 4.4 of RFC 3461
[RFC3461].
All of these tests fail unconditionally if the specified envelope
parameter does not exist for the current message or recipient.
The envelope test's ADDRESS-PART argument assumes the string being
tested has the syntax of an email address. None of the new envelope
parts defined here have address syntax, accordingly, it is an error
to specify an ADDRESS-PART argument in conjunction with these new
envelope parts.
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The "relational" extension [RFC5231] adds a match type called
":count". The count of an envelope test of with an envelope-part of
"orcpt", "ret", and "envid" is 1 if the corresponding SMTP parameter
is present and 0 otherwise. The count of an envelope test with an
envelope-part of "notify" is equal to the number of notification
conditions specified and 0 if the NOTIFY parameter is not present.
5. Dsn-redirect extension
The "dsn-redirect" extension does not define any new tests or
actions, rather, it adds two new arguments, NOTIFY and RET, to the
redirect action defined in Section 4.2 of [RFC5228]. This updates
the usage description for redirect to:
Usage: redirect [NOTIFY] [RET] <address: string>
The syntax for the NOTIFY and RET arguments are:
NOTIFY = ":notify" notify-value
notify-value = DQUOTE notify-esmtp-value DQUOTE
RET = ":ret" ret-value
ret-value = DQUOTE ("FULL" / "HDRS") DQUOTE
The notify-esmtp-value production is defined in Section 4.1 of
[RFC3461].
When these arguments are specified, they set the corresponding NOTIFY
ESMTP RCPT TO and RET ESMTP MAIL FROM parameters, respectively.
These parameters are only available when the delivery status
notification (DSN) ESMTP extension is available; they are simply
ignored and MUST NOT cause an error if the DSN extension is
unavailable.
6. Security Considerations
The dsn-envelope extension provides access to additional message
envelope information. This is not believed to raise any additional
security issues beyond those for the Sieve "envelope" test.
The dsn-redirect extension allows specification of the delivery
status notification's NOTIFY parameter which can cause the generation
of notification messages that might otherwise not be generated,
especially if notification in the event of successful delivery is
required. Sites which limit the ability to request success
notifications will also need to restrict the ability to request then
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using the dsn-redirect extension.
All of the security considerations given in the base Sieve
specification also apply to this extension.
7. IANA Considerations
The following template specifies the IANA registration of the Sieve
extension specified in this document:
To: iana@iana.org
Subject: Registration of new Sieve extensions
Capability name: dsn-envelope
Description: The "dsn-envelope" extension extends the envelope
test to allow checking of information associated
with the DSN ESMTP extension defined in RFC 3461.
RFC number: RFC XXXX
Contact address: Sieve discussion list <ietf-mta-filters@imc.org>
Capability name: dsn-envelope
Description: The "dsn-redirect" extension extends the redirect
action to allow specification of the NOTIFY and
RET ESMTP parameters associated with the DSN SMTP
extension defined in RFC 3461.
RFC number: RFC XXXX
Contact address: 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.
8. References
8.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3461] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service
Extension for Delivery Status Notifications (DSNs)",
RFC 3461, January 2003.
[RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
Language", RFC 5228, January 2008.
[RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering:
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Relational Extension", RFC 5231, January 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
8.2. Informative references
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003.
Author's Address
Ned Freed
Sun Microsystems
800 Royal Oaks
Monrovia, CA 91016-6347
USA
Phone: +1 909 457 4293
Email: ned.freed@mrochek.com
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