Network Working Group                                           N. Freed
Internet-Draft                                          Sun Microsystems
Expires: July 19, September 25, 2009                                  January 15,                               March 24, 2009

  Sieve Email Filtering:  Delivery Status Notifications Extension
                      draft-freed-sieve-notary-04 and Deliver-By
                               Extensions
                      draft-freed-sieve-notary-05

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Abstract

   This document describes the "envelope-dsn" "envelope-dsn", "redirect-dsn",
   "envelope-deliverby", and "redirect-dsn" "redirect-deliverby" extensions to the
   Sieve email filtering language.  The "envelope-dsn"
   extension provides and "envelope-
   deliverby" extensions provide access to additional envelope
   information provided by the delivery status notification extension to and
   deliver-by SMTP defined in RFC
   3461. extensions.  The "redirect-dsn" extension extends and "redirect-
   deliverby" extensions extend Sieve's redirect action to provide
   control over delivery status notification parameters. and deliver-by parameters,
   respectively.

Change History (to be removed prior to publication as an RFC

   Fixed several typos.

   Changed name of extension from notary to envelope-dsn.

   Added the redirect-dsn extension.

   Updated references.

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

   Fleshed out the 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.

   Added the two deliver-by extensions.

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 "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 "envelope-deliverby" extension extends the envelope
   test to allow access to the additional envelope fields defined by the
   deliver-by SMTP extension defined in [RFC2852].

   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 "redirect-dsn"
   extension extends redirect to allow specification of some fields
   defined by the delivery status notification SMTP extension.
   "redirect-deliverby" in turn provides the ability to set a time limit
   for delivery as specified in RFC 2852 [RFC2852].

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] [RFC5234], and
   refers to the ABNF production productions 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 "envelope-dsn" "envelope-dsn", "redirect-dsn", "envelope-deliverby",
   and "redirect-dsn". "redirect-deliverby".

4.  envelope-dsn extension  Envelope-dsn Extension

   The "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 the 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 test 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 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 parameter is multivalued and the
   notify envelope-part turns this into a list of values makes it easy
   to check to see if a given value is present without having to worry
   about other values:

   require ["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", "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 always contains an address type indicator
   prefix in addition to an address, which must be taken into account in
   any tests:

   require ["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.  redirect-dsn extension  Envelope-deliverby Extension

   The "redirect-dsn" "envelope-deliverby" extension does not define any new tests or
   actions, rather, it adds two new arguments, NOTIFY and RET, three values to the
   redirect action list of possible (case-
   insensitive) envelope-part strings defined in Section 4.2 5.4 of [RFC5228].  This updates
   [RFC5228]:

   bytime  Match the usage description for redirect to:
   [
   Usage:   redirect [:notify "value"] [:ret "FULL"|"HDRS"]
                     <address: string>

   The syntax for initial integer part of 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 deliver-by extension's
      BY parameter specified in Section 4.1 the SMTP MAIL FROM command.

   bymde  Match a string computed from the by-mode part of
   [RFC3461].

   When these arguments the
      deliver-by extension's BY parameter.  The possible values are specified, they set
      "notify" and "return", which correspond to the corresponding NOTIFY
   ESMTP RCPT TO BY parameter mode
      specifier characters "N" and RET ESMTP MAIL FROM parameters, "R" respectively.
   These parameters are only available when

   bytrace  Match the delivery status
   notification (DSN) ESMTP extension is available.  When trace modifier computed from the DSN
   extension is not available, by-trace modifier
      on the parameters MUST be ignored and MUST
   NOT cause an error.

5.1.  Example

   One deliver-by extension's BY parameter.  The possible use of :notify on redirect is values
      are "trace" and "" (the empty string).  These values correspond to combine
      the copy
   extension [RFC3894] with the ability to suppress nondelivery
   notifications to generate a private copy presence or absence of the by-trace "T" modifier respectively.

   All of these tests fail unconditionally if the BY SMTP MAIL FROM
   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 with an envelope-part of
   "bytime", "bymode", and "bytrace" is 1 if the BY parameter is present
   and 0 otherwise.

   It should be noted that the deliver-by by-time is decremented as the
   message passes through the transport infrastructure.  Accordingly, it
   is not possible to tell what the message originator set the value to,
   only the amount of time remaining at the moment the sieve is run.

5.1.  Example

   As noted above, this extension does not provide access to the
   originator's initial by-time setting for the simple reason that this
   information is not part of the envelope.  It can, however, be used to
   check and see if the message was delivered within the alloted time.

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

   # Check to see if this message didn't make it in the time alloted by
   # the originator.
   if envelope :value "eq" :comparator "i;ascii-numeric" "bytime" "0"
   {
       # do whatever
   }

6.  redirect-dsn extension

   The "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 "value"] [:ret "FULL"|"HDRS"]
                     <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 arguments are only honored if the delivery status notification
   (DSN) ESMTP extension is available.  When the DSN extension is not
   available, these arguments MUST be ignored and MUST NOT cause an
   error.

6.1.  Example

   One possible use of :notify on redirect is to combine 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: 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";
   }

7.  redirect-deliverby extension

   The "redirect-deliverby" extension does not define any new tests or
   actions, rather, it adds three new arguments, BYTIME, BYMODE, and
   BYTRACE, to the redirect action defined in Section 4.2 of [RFC5228].
   This updates the usage description for redirect to:
   [
   Usage:   redirect [:bytime <limit: number>
                      [:bymode "notify"|"return"] [:bytrace]]
                     <address: string>

   :bytime specifies the number of seconds within which the message
   should be delivered. :bymode specifies whether a notification should
   be sent or the message simply returned if the time limit is exceeded.
   The default is "return" if :bymode is not specified.  See The
   semantics of delivery time limits are specified and discussed at
   length in [RFC2852].

   It is an error to specify :bymode and :bytrace without :bytime.

   When these arguments are specified, they are used to construct the
   corresponding BY ESMTP MAIL FROM parameter.  The :bytime value
   becomes the by-time, the :bymode becomes the by-mode value, and
   :bytrace sets the by-trace modifier.  If the deliver-by extension is
   unavailable, the handling of reredirected message MUST conform to the
   semantics specified in [RFC2852] section 4.1.4 for relaying to a
   server that does not support the deliver-by SMTP extension.

7.1.  Example

   The obvious use of "redirect-deliverby" is to specify a limit on
   delivery attempts for a redirected message:

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

   # Make Send a private copy of messages from user@example.com to my cell phone, time out after 10 minutes
   if address "from" "user@example.com"
   {
       redirect :copy :notify "NEVER" "elsewhere@example.com"; :bytime 600 "cellphone@example.com";
   }

6.

8.  Security Considerations

   The envelope-dsn extension provides and envelope-deliverby extensions provide access to
   additional message envelope information.  This is not believed to
   raise any additional security issues beyond those for the Sieve
   "envelope" test.

   The 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 redirect-dsn extension.

   Similarly, the redirect-deliverby extension is used to control how
   long the transport infrastructure will continue to attempt to deliver
   a message before giving up, which could result in the generation of
   additional notification messages.  While the underlying Deliver-By
   extension does have a minimum by-time limit, sites may wish to impose
   additional limits on the minimum by-time allowed in a redirect
   action.

   All of the security considerations given in the base Sieve
   specification also apply to this extension.

7.

9.  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: envelope-dsn
    Description:     The "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: envelope-deliverby
    Description:     The "envelope-deliverby" extension extends the
                     envelope test to allow checking of information
                     associated with the Deliver-By ESMTP extension
                     defined in RFC 2852.
    RFC number:      RFC XXXX
    Contact address: Sieve discussion list <ietf-mta-filters@imc.org>

    Capability name: redirect-dsn
    Description:     The "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>

    Capability name: redirect-deliverby
    Description:     The "redirect-deliverby" extension extends the
                     redirect action to allow specification of the BY
                     ESMTP parameter associated with the Deliver-By SMTP
                     extension defined in RFC 2852.
    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.

10.  References

8.1.

10.1.  Normative references

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2852]  Newman, D., "Deliver By SMTP Service Extension", RFC 2852,
              June 2000.

   [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.

10.2.  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, Andrew
   McKeon, Alexey Melnikov, Chris Newman, Aaron Stone, 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