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Internet Engineering Task Force (IETF)                          N. FreedRequest for Comments: 6009                                        OracleCategory: Standards Track                                   October 2010ISSN: 2070-1721Sieve Email Filtering:Delivery Status Notifications and Deliver-By ExtensionsAbstract   This document describes the "envelope-dsn", "redirect-dsn",   "envelope-deliverby", and "redirect-deliverby" extensions to the   Sieve email filtering language.  The "envelope-dsn" and "envelope-   deliverby" extensions provide access to additional envelope   information provided by the delivery status notification (DSN) and   Deliver-By SMTP extensions, respectively.  The "redirect-dsn" and   "redirect-deliverby" extensions extend Sieve's redirect action to   provide control over delivery status notification and Deliver-By   parameters, respectively.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6009.Freed                        Standards Track                    [Page 1]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .32.  Conventions Used in This Document  . . . . . . . . . . . . . .33.  Capability Identifiers . . . . . . . . . . . . . . . . . . . .44.  Envelope-dsn Extension . . . . . . . . . . . . . . . . . . . .44.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .55.  Envelope-deliverby Extension . . . . . . . . . . . . . . . . .65.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .76.  redirect-dsn Extension . . . . . . . . . . . . . . . . . . . .96.1.  MAIL FROM Address Selection  . . . . . . . . . . . . . . .96.2.  Example  . . . . . . . . . . . . . . . . . . . . . . . . .97.  redirect-deliverby Extension . . . . . . . . . . . . . . . . .107.1.  MAIL FROM Address Selection  . . . . . . . . . . . . . . .117.2.  Example  . . . . . . . . . . . . . . . . . . . . . . . . .118.  Security Considerations  . . . . . . . . . . . . . . . . . . .119.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .1210. References . . . . . . . . . . . . . . . . . . . . . . . . . .1310.1. Normative References . . . . . . . . . . . . . . . . . . .1310.2. Informative References . . . . . . . . . . . . . . . . . .14Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . .15Freed                        Standards Track                    [Page 2]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 20101.  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 [RFC5321] 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 notifications (DSNs) specified inRFC 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 inRFC 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 fromSection 1.1 of [RFC5228].  The nature and   handling of Sieve errors are described inSection 2.10.6 of   [RFC5228].   This document uses the ABNF notation specified in [RFC5234], and   refers to the notify-esmtp-value ABNF production defined inSection 4.1 of [RFC3461].Freed                        Standards Track                    [Page 3]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 20103.  Capability Identifiers   The capability strings associated with the extensions defined in this   document are "envelope-dsn", "redirect-dsn", "envelope-deliverby",   and "redirect-deliverby".4.  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 inSection 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 test to succeed.  The syntax and semantics of      the NOTIFY parameter are defined inSection 4.1 of RFC 3461      [RFC3461] .  Currently, the possible notification condition values      are "NEVER", "SUCCESS", "FAILURE", and "DELAY".  Note that the      value "NEVER" is never combined with any other value.   orcpt -  Match the original recipient, or ORCPT, value associated      with the TO address used in the SMTP RCPT TO command that resulted      in this message getting delivered to this user, with xtext      encoding removed.  The syntax and semantics of the ORCPT parameter      are defined inSection 4.2 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 inSection 4.3 of RFC 3461 [RFC3461].  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 inSection 4.4 of      RFC 3461 [RFC3461].   The envelope test fails unconditionally for each of these envelope-   part strings if the specified envelope parameter does not exist for   the current message or recipient.Freed                        Standards Track                    [Page 4]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   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:Freed                        Standards Track                    [Page 5]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   require ["envelope", "envelope-dsn"];   # See if the orcpt is anRFC822 address in the example.com   # domain   if envelope :matches "orcpt" "rfc822;*@example.com"   {       # do whatever   }5.  Envelope-deliverby Extension   The "envelope-deliverby" 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 inSection 5.4 of   [RFC5228] and an optional :zone tagged argument.  This updates the   usage description for envelope to:   Usage:   envelope [COMPARATOR] [ADDRESS-PART]                     [MATCH-TYPE] [:zone <time-zone: string>]                     <envelope-part: string-list>                     <key-list: string-list>   These new envelope parts correspond to the new MAIL FROM parameters   defined inSection 4 of [RFC2852].  They are:   bytimeabsolute -  Match the current value of the initial integer part      of the Deliver-By extension's BY parameter on the SMTP MAIL FROM      command, converted into an absolute time represented in restricted      ISO 8601 format.  The restricted ISO 8601 format is specified by      the date-time ABNF production given in[RFC3339], Section 5.6,      with the added restrictions that the letters "T" and "Z" MUST be      in upper case, and a time zone offset of zero MUST be represented      by "Z" and not "+00:00".   bytimerelative -  Match the current value of the initial integer part      of the Deliver-By extension's BY parameter specified in the SMTP      MAIL FROM command.   bymode -  Match a string computed from the by-mode part of the      Deliver-By extension's BY parameter.  The possible values are      "notify" and "return", which correspond to the BY parameter mode      specifier characters "N" and "R", respectively.   bytrace -  Match the trace modifier computed from the by-trace      modifier on the Deliver-By extension's BY parameter.  The possible      values are "trace" and "" (the empty string).  These values      correspond to the presence or absence of the by-trace "T"      modifier, respectively.Freed                        Standards Track                    [Page 6]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   The envelope test fails unconditionally for each of these envelope-   part strings if the BY SMTP MAIL FROM parameter does not exist for   the current message or recipient.   The new :zone argument specifies a time zone offset string that any   bytimeabsolute value is to be shifted to prior to testing. :zone has   no effect on envelope-parts other than bytimeabsolute.  The value of   the time zone offset string MUST be an offset relative to UTC with   the following syntax:   time-zone  =  ( "+" / "-" ) 4DIGIT   The "+" or "-" indicates whether the time-of-day is ahead of (i.e.,   east of) or behind (i.e., west of) UTC.  The first two digits   indicate the number of hours difference from Universal Time, and the   last two digits indicate the number of minutes difference from   Universal Time.  Note that this agrees with the [RFC5322] format for   time zone offsets, not the ISO 8601 format.  The local time zone MUST   be used for bytimeabsolute if the :zone argument is omitted.   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 is important to note 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 can be determined.  Additionally, note that   bytimerelative values can be negative, making it necessary to either   perform additional checks or else use a comparator that, unlike   i;ascii-numeric, is capable of handling signed integers.5.1.  Examples   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 allotted time.   Note the additional check to see if the value is negative:Freed                        Standards Track                    [Page 7]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   require ["envelope", "envelope-deliverby", "relational",            "comparator-i;ascii-numeric"];   # Check to see if this message didn't make it in the time allotted by   # the originator.   if anyof (envelope :contains "bytimerelative" "-",             envelope :value "eq" :comparator "i;ascii-numeric"                      "bytimerelative" "0")   {       # do whatever   }   This operation can be done more simply if the date [RFC5260] and   variables [RFC5229] extensions are available:   require ["envelope", "envelope-deliverby", "relational", "date",            "variables"];   # Check to see if this message didn't make it in the time allotted by   # the originator.   if currentdate :matches "iso8601" "*" {       set "cdate" "${0}";       if envelope :value "ge" "bytimeabsolute" "${cdate}" {           # do whatever       }   }   Note that there is no need to force the use of a particular time zone   since both currentdate and the bytimeabsolute value are required to   default to the local time zone.  A similar check could be written   using :zone if the action taken depends on having the by-time   represented in a particular zone:   require ["envelope", "envelope-deliverby", "relational", "date",            "variables"];   # If the message didn't make it in time, file it according to when it   # should have been received   if envelope :matches :zone "+0000" "bytimeabsolute" "*T*:*:*" {       set "bdate" "${0}";       set "bhour" "${2}";       if currentdate :zone "+0000" :value "lt" "iso8601" "${bdate}")           fileinto "missed-${bhour}";       }   }Freed                        Standards Track                    [Page 8]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 20106.  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 inSection 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 ("NEVER" / notify-esmtp-list) DQUOTE   notify-esmtp-list = notify-list-element *("," notify-list-element)   RET = ":ret" ret-value   ret-value = DQUOTE ("FULL" / "HDRS") DQUOTE   The notify-list-element ABNF production is defined inSection 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.  MAIL FROM Address SelectionRFC 5228 does not require that any particular envelope sender address   be associated with redirected messages.  However, the redirect-dsn   extension isn't terribly useful if the place where the delivery   status notifications are sent isn't known.  Accordingly, when either   :notify or :ret is specified and the envelope sender address isn't   empty, implementations MUST set the envelope sender address to the   address of the sieve owner.6.2.  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:Freed                        Standards Track                    [Page 9]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   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 inSection 4.2 of [RFC5228].   This updates the usage description for redirect to:   Usage:   redirect [:bytimerelative <rlimit: number> /                      :bytimeabsolute <alimit:string>                      [:bymode "notify"|"return"] [:bytrace]]                     <address: string>   :bytimerelative specifies the number of seconds within which the   message should be delivered.  This parameter does not allow   specification of negative values; it should not be necessary to   specify such values in this context. :bytimeabsolute specifies an   absolute time limit on delivery.  The limit in this case is specified   in the restricted ISO 8601 format specified by the date-time ABNF   production given in [RFC3339].   :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. :bytrace, if specified,   activates message tracing.   The semantics of delivery time limits and these parameters are   specified and discussed at length in [RFC2852].   It is an error to specify either :bymode or :bytrace without either   :bytimeabsolute or :bytimerelative.   When these arguments are specified, they are used to construct the   corresponding BY ESMTP MAIL FROM parameter.  The :bytimeabsolute or   :bytimerelative 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 the redirected   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.Freed                        Standards Track                   [Page 10]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 20107.1.  MAIL FROM Address SelectionRFC 5228 does not require that any particular envelope sender address   be associated with redirected messages.  However, the redirect-   deliverby extension, like the redirect-dsn extension, isn't terribly   useful if the place where any delivery status notifications are sent   isn't known.  Accordingly, when either :bytimeabsolute or   :bytimerelative is specified and the envelope sender address isn't   empty, implementations MUST set the envelope sender address to the   address of the sieve owner.7.2.  Example   The obvious use of "redirect-deliverby" is to specify a limit on   delivery attempts for a redirected message:   require ["copy", "redirect-deliverby"];   # Send a copy to my cell phone, time out after 10 minutes   if address "from" "user@example.com"   {       redirect :copy :bytimerelative 600 "cellphone@example.com";   }   Limits on delivery after a particular time of day may also be   constructed:   require ["copy", "redirect-deliverby", "date", "variables",            "relational", "comparator-i;ascii-numeric"];   # Send a copy to my cell phone to be delivered before 10PM   if currentdate :value "lt"                  :comparator "i;ascii-numeric" "hour" "22"   {       if currentdate :matches "date" "*" {set "date" "${0}";}       if currentdate :matches "zone" "*" {set "zone" "${0}";}       redirect :copy :bytimeabsolute "${date}T20:00:00${zone}"                :bymode "return" "cellphone@example.com";   }8.  Security Considerations   The envelope-dsn 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.Freed                        Standards Track                   [Page 11]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   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 that 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.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 inRFC 3461.    RFC number:RFC 6009    Contact address: Sieve discussion list <sieve@ietf.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 inRFC 2852.    RFC number:RFC 6009    Contact address: Sieve discussion list <sieve@ietf.org>Freed                        Standards Track                   [Page 12]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010    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 inRFC 3461.    RFC number:RFC 6009    Contact address: Sieve discussion list <sieve@ietf.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 inRFC 2852.    RFC number:RFC 6009    Contact address: Sieve discussion list <sieve@ietf.org>    This information has been added to the list of Sieve extensions    available fromhttp://www.iana.org.10.  References10.1.  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.   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the              Internet: Timestamps",RFC 3339, July 2002.   [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.   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol",RFC 5321,              October 2008.Freed                        Standards Track                   [Page 13]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010   [RFC5322]  Resnick, P., Ed., "Internet Message Format",RFC 5322,              October 2008.10.2.  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.   [RFC5229]  Homme, K., "Sieve Email Filtering: Variables Extension",RFC 5229, January 2008.   [RFC5260]  Freed, N., "Sieve Email Filtering: Date and Index              Extensions",RFC 5260, July 2008.Freed                        Standards Track                   [Page 14]

RFC 6009          Sieve DSNs and Deliver-By Extensions      October 2010Appendix A.  Acknowledgements   Cyrus Daboo, Derek Diget, Philip Guenther, Arnt Gulbrandsen, Tero   Kivinen, Barry Leiba, Andrew McKeon, Alexey Melnikov, Chris Newman,   Aaron Stone, and Alexandros Vellis provided helpful suggestions and   corrections.Author's Address   Ned Freed   Oracle   800 Royal Oaks   Monrovia, CA  91016-6347   USA   EMail: ned.freed@mrochek.comFreed                        Standards Track                   [Page 15]