Network Working Group                                           N. Freed
Internet-Draft                                          Sun Microsystems
Expires: May 21, July 19, 2009                                  January 15, 2009                                  November 17, 2008

    Sieve Email Filtering:  Delivery Status Notifications Extension
                      draft-freed-sieve-notary-02
                      draft-freed-sieve-notary-03

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Abstract

   This document describes the "dsn-envelope" "envelope-dsn" and "dsn-redirect" "redirect-dsn"
   extensions to the Sieve email filtering language.  The "dsn-envelope" "envelope-dsn"
   extension provides access to additional envelope information provided
   by the delivery status notification extension to SMTP defined in RFC
   3461.  The "dsn-redirect" "redirect-dsn" 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. envelope-dsn.

   Added the dsn-redirect redirect-dsn extension.

   Updated references.

   Added a note about the use of ADDRESS-PART arguments with the new
   envelope-part strings defined by the dsn-envelope envelope-dsn extension.

   Fleshed out the dsn-redirect redirect-dsn extension.

   Changed document title to agree with new extension names.

   Added some examples.

   Fixed more typos.

   Changed dsn-envelope and dsn-redirect to envelope-dsn and redirect-
   dsn, respectively.

   Added a redirect-dsn example.

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"
   "envelope-dsn" 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" "redirect-dsn"
   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 [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].

3.  Capability Identifier

   The capability strings associated with the extensions defined in this
   document are "dsn-envelope" "envelope-dsn" and "dsn-redirect". "redirect-dsn".

4.  Dsn-envelope  envelope-dsn extension

   The "dsn-envelope" "envelope-dsn" 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.

   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.

4.1.  Examples

   The fact that the notify envelope-part operates on a list of values
   makes it easy to check to see if a given value is present without
   havingt
   having to worry about other values:

   require ["envelope", "dsn-envelope"]; "envelope-dsn"];

   # Check whether SUCCESS notifications were requested,
   # irrespective of any other requests that were made
   if envelope "notify" "SUCCESS"
   {
       # do whatever
   }

   Checking to see if a given request is the only one present is a
   little trickier, however:

   require ["envelope", "dsn-envelope", "envelope-dsn", "relational",
            "comparator-i;ascii-numeric"];

   # Check whether only FAILURE notifications were requested
   if allof ( envelope "notify" "FAILURE",
              envelope :comparator "i;ascii-numeric"
                       :count "eq" "notify" "1"
            )
   {
       # do whatever
   }

   The orcpt envelope-part contains an address type indicator in
   addition to an address, which must be taken into account:

   require ["envelope", "dsn-envelope"]; "envelope-dsn"];

   # See if the orcpt is an RFC822 address in the example.com
   # domain
   if envelope :matches "orcpt" "rfc822;*@example.com"
   {
       # do whatever
   }

5.  Dsn-redirect  redirect-dsn extension

   The "dsn-redirect" "redirect-dsn" 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.

5.1.  Example

   One possible use of :notify on redirect is to ccmbine the copy
   extension [RFC3894] with the ability to suppress nondelivery
   notifications to generate a private copy of selected messages with no
   side effects or error notifications:

   require ["copy", "redirect-dsn"];

   # Make a private copy of messages from user@example.com
   if address "from" "user@example.com"
   {
       redirect :copy :notify "NEVER" "elsewhere@example.com";
   }

6.  Security Considerations

   The dsn-envelope envelope-dsn 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 redirect-dsn 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 them
   using the dsn-redirect redirect-dsn 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 envelope-dsn
      Description:     The "dsn-envelope" "envelope-dsn" 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-redirect redirect-dsn
      Description:     The "dsn-redirect" "redirect-dsn" 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:
              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.

   [RFC3894]  Degener, J., "Sieve Extension: Copying Without Side
              Effects", RFC 3894, October 2004.

Appendix A.  Acknowledgements

   Cyrus Daboo, Derek Diget, Philip Guenther, Arnt Gulbrandsen, Alexey
   Melnikov, and Alexandros Vellis provided helpful suggestions and
   corrections.

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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