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Versions: (draft-showalter-sieve-vacation) 00 01 02 03 04 05 06 07 RFC 5230

SIEVE Email Filtering Working                               T. Showalter
Group                                                                 ??
Internet-Draft                                                  N. Freed
Expires: September 15, 2005                             Sun Microsystems
                                                          March 14, 2005


               Sieve Email Filtering:  Vacation Extension
                      draft-ietf-sieve-vacation-00

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on September 15, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes an extension to the Sieve email filtering
   language for an autoresponder similar to that of the Unix "vacation"
   command for replying to messages.  Various safety features are
   included to prevent problems such as message loops.




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

   Changes from draft-showalter-sieve-vacation-06.txt:
   1.  Updated to XML source.
   2.  Added :from parameter.
   3.  Added more detailed description of :subject parameter
   4.  Fixed various minor typos.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Capability Identifier  . . . . . . . . . . . . . . . . . . . .  3
   3.  Vacation Action  . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1   Days Parameter . . . . . . . . . . . . . . . . . . . . . .  3
     3.2   Previous Response Tracking . . . . . . . . . . . . . . . .  4
     3.3   Subject and from parameters  . . . . . . . . . . . . . . .  5
     3.4   MIME Parameter . . . . . . . . . . . . . . . . . . . . . .  5
     3.5   Address Parameter and Limiting Replies to Personal
           Messages . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.6   Restricting Replies to Automated Processes and Mailing
           Lists  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.7   Interaction with Other Sieve Actions . . . . . . . . . . .  6
     3.8   Examples . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Response Message Generation  . . . . . . . . . . . . . . . . .  7
     4.1   SMTP MAIL FROM address . . . . . . . . . . . . . . . . . .  7
     4.2   Subject Parameter  . . . . . . . . . . . . . . . . . . . .  7
     4.3   In-Reply-To and References . . . . . . . . . . . . . . . .  7
     4.4   From . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.5   To . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.6   Auto-submitted . . . . . . . . . . . . . . . . . . . . . .  7
     4.7   Message Body . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Relationship to Recommendations for Automatic Responses to
       Electronic Mail  . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     8.1   Normative References . . . . . . . . . . . . . . . . . . .  8
     8.2   Informative References . . . . . . . . . . . . . . . . . .  9
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  9
   A.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
       Intellectual Property and Copyright Statements . . . . . . . . 10










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1.  Introduction

   This is an extension to the Sieve language defined by [RFC3028] for
   notification that messages will not be immediately answered.

   Conventions for notations are as in [RFC3028] section 1.1.

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", "CAN", and
   "MAY" in this document are to be interpreted as defined in [RFC2119].

2.  Capability Identifier

   Sieve implementations that implement vacation have an identifier of
   "vacation" for use with the capability mechanism.

3.  Vacation Action

   Syntax:   vacation [":days" number] [":subject" string] [":from" string]
                      [":addresses" string-list] [":mime"] <reason: string>

   The "vacation" action implements a vacation autoresponder similar to
   the vacation command available under many versions of Unix.  Its
   purpose is to provide correspondents with notification that the user
   is away for an extended period of time and that they should not
   expect quick responses.

   "Vacation" is used to respond to a message with another message.
   Vacation's messages are always addressed to the Return-Path address
   (that is, the envelope from address) of the message being responded
   to.

3.1  Days Parameter

   The ":days" argument is used to specify the period in which addresses
   are kept and are not responded to, and is always specified in days.
   The minimum value used for this parameter is normally 1.  Sites MAY
   define a different minimum value.  Sites MAY also define a maximum
   days value, which MUST be greater than 7, and SHOULD be greater than
   30.

   If ":days" is omitted, the default value is either 7 or the minimum
   value (as defined above), whichever is greater.

   If the parameter given to ":days" is less than the minimum value,
   then the minimum value is used instead.

   If ":days" exceeds the site-defined maximum, the site-defined maximum
   is used instead.



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3.2  Previous Response Tracking

   "Vacation" keeps track of all of the responses it has sent to each
   address in some period (as specified by the :days optional argument).
   If vacation has not previously sent the response to this address
   within the given time period, it sends the "reason" argument to the
   SMTP MAIL FROM address of the message that is being responded to.
   (The SMTP MAIL FROM address should be available in the Return-path:
   header field if Sieve processing occurs after final delivery.)

   Vacation responses are not just per address, but are per address per
   set of arguments to the vacation command.  For instance, If
   coyote@desert.example.org sends mail to roadrunner@acme.example.com,
   once with the subject "Cyrus bug" and once with the subject "come
   over for dinner", and roadrunner@acme.example.com has the script
   below, coyote@desert.example.org would receive two responses, once
   with the first message, once with the second.

   Example:  require "vacation";
             if subject :contains "cyrus" {
                       vacation "I'm out -- send mail to cyrus-bugs";
             } else {
                       vacation "I'm out -- call me at 304 555 1212";
             }

   In the above example, coyote@desert.example.org gets the second
   message despite having gotten the first one because separate vaca-
   tion responses have been triggered.  This behavior is REQUIRED.

   The "per set of arguments" described above is intended to ensure that
   a respondee gets all of the various possible responses, not merely
   the first one.  So, if the :subject or :mime parameters would result
   in a different message, a different message MUST be sent by the
   implementation.

   If a script is changed, implementations MAY reset the records of who
   has been responded to and when they have been responded to.
   Alternatively, implementations can store records of who has received
   which message, perhaps by storing a hash of the message and the
   recipient.

   Implementations are free to limit the number of remembered responses,
   provided the limit is no less than 1000.

   Implementations SHOULD make the limit no less than 1000 per vacation
   command if using the hash algorithm described above.  When limiting
   the number of tracked responses, implementations SHOULD discard the
   oldest ones first.



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3.3  Subject and from parameters

   The ":subject" parameter specifies a subject line to attach to any
   vacation response that is generated.  UTF-8 characters can be used in
   the string argument; implementations MUST convert the string to
   [RFC2047] encoded words if non-ASCII characters are present.
   Implementations SHOULD insert an apppropriate default subject line if
   no :subject parameter is specified.

   A ":from" parameter MAY be used to specify an alternate address to
   use in the From field of vacation messages.  The string must specify
   a valid [RFC2822] mailbox-list.  Implementations SHOULD check the
   syntax and generate an error when a syntactically invalid ":from"
   parameter is specified.  Implementations MAY also impose security
   restrictions on what addresses can specified in a ":from" parameter;
   it is suggested that values which fail such a security check simply
   be ignored rather than causing the vacation action to fail.

3.4  MIME Parameter

   The ":mime" parameter, if supplied, specifies that the reason string
   is, in fact, a MIME part, including MIME headers (see section 2.4.2.4
   of [RFC3028]).

   If the optional :mime parameter is not supplied, the reason string is
   considered to be a UTF-8 string.

3.5  Address Parameter and Limiting Replies to Personal Messages

   "Vacation" MUST NOT respond to a message unless the user's email
   address is in a "To", "Cc", "Bcc", "Resent-To", "Resent-Cc", or
   "Resent-Bcc" line of the original message.  Implementations are
   assumed to know the user's email address, but users may have
   additional addresses beyond the control of the local mail system.

   Users can supply additional mail addresses that are theirs with the
   ":addresses" argument, which takes a string-list listing additional
   addresses that a user might have.  These addresses are considered in
   addition to the addresses that the implementation knows.

3.6  Restricting Replies to Automated Processes and Mailing Lists

   Implementations MUST have a list of addresses that "vacation" MUST
   NOT send mail to.  However, the contents of this list are
   implementation defined.  The purpose of this list is to stop mail
   from going to addresses used by system daemons that would not care if
   the user is actually reading her mail.




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   Implementations are encouraged, however, to include well-known
   addresses like "MAILER-DAEMON", "LISTSERV", "majordomo", and other
   addresses typically used only by automated systems.  Additionally,
   addresses ending in "-request" or beginning in "owner-", i.e.,
   reserved for mailing list software, are also suggested.

   Implementors may take guidance from [RFC2142], but should be careful.
   Some addresses, like "POSTMASTER", are generally actually managed by
   people, and people do care if the user is going to be unavailable.

   Implementations SHOULD NOT not to respond to any message with a
   header that begins with "List-".

   Implementations SHOULD NOT respond to any message that has an
   "Auto-submitted" header field with a value other than "no".  This
   header field is described in [RFC3834].

3.7  Interaction with Other Sieve Actions

   Vacation does not affect Sieve's implicit keep action.

   Vacation can only be executed once per script.  A script will fail if
   two vacation actions are used.

   Implementations MUST NOT consider vacation used with discard, keep,
   fileinto, or redirect an error.

3.8  Examples

   Here is a simple use of vacation.

   Example:
                  require "vacation";
                  vacation :days 23 :addresses ["tjs@example.edu",
                                         "ts4z@landru.example.edu"]
                         "I'm away until October 19.
                          If it's an emergency, call 911, I guess." ;

   By mingling vacation with other rules, users can do something more
   selective.

   Example:  require "vacation";
                  if header :contains "from" "boss@example.edu" {
                                        redirect "pleeb@isp.example.org";
                  } else {
                                        vacation "Sorry, I'm away, I'll read your
                                           message when I get around to it.";
                  }



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4.  Response Message Generation

   This section details the requirements for the generated response
   message.

   It is worth noting that the input message and arguments may be in
   UTF-8, and that implementations MUST deal with UTF-8 input, although
   implementations MAY transcode to other character sets as regional
   taste dictates.

4.1  SMTP MAIL FROM address

   The SMTP MAIL FROM address of the message envelope SHOULD be set to
   <>.  NOTIFY=NEVER SHOULD also be set in the RCPT TO line during the
   SMTP transaction if the NOTARY SMTP extension is available.

4.2  Subject Parameter

   Users can specify the subject of the reply with the ":subject"
   parameter.  If the :subject parameter is not supplied, then the
   subject is generated as follows: The subject is set to the characters
   "Re: " followed by the original subject with all leading occurrence
   of the characters "Re: " stripped off.

4.3  In-Reply-To and References

   Replies MUST have the In-Reply-To field set to the Message-ID of the
   original message, and the References field must be updated with the
   Message-ID of the original message.

   If the original message lacks a Message-ID, an In-Reply-To need not
   be generated, and References need not bne changed.

4.4  From

   Unless explicitly overridden with a :from parameter, the From field
   SHOULD be set to the address of the owner of the Sieve script.

4.5  To

   The To field SHOULD be set to the address of the recipient of the
   response.

4.6  Auto-submitted

   An Auto-Submitted field with a value of "auto-replied" SHOULD be
   included in the message header of any vacation message sent.




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4.7  Message Body

   The body of the message is taken from the reason string in the
   vacation command.

5.  Relationship to Recommendations for Automatic Responses to
   Electronic Mail

   The vacation extension implements a "Personal Responder" in the
   terminology defined in [RFC3834].  Care has been taken in this
   specification to comply with the recommendations [RFC3834] makes in
   regards to how personal responders should behave.

6.  Security Considerations

   It is critical that implementations correctly implement the
   limitations described above.  Replies MUST NOT be sent out in
   response to messages not sent directly to the user, and replies MUST
   NOT be sent out more often than the :days argument states.

   Security issues associated with mail auto-responders are fully
   discussed in the security consideration section of [RFC3834].

7.  IANA Considerations

   The following template specifies the IANA registration of the
   vacation Sieve extension specified in this document:

   To: iana@iana.org
   Subject: Registration of new Sieve extension


   Capability name: vacation
   Capability keyword: vacation
   Capability arguments: N/A
   Standards Track/IESG-approved experimental RFC number: this RFC
   Person and email address to contact for further information:
       Tim Showalter
       E-Mail: tjs@psaux.com

   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

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail



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              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [RFC2047]  Moore, K., "MIME (Multipurpose Internet Mail Extensions)
              Part Three: Message Header Extensions for Non-ASCII Text",
              RFC 2047, November 1996.

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

   [RFC2822]  Resnick, P., "Internet Message Format", RFC 2822, April
              2001.

   [RFC3028]  Showalter, T., "Sieve: A Mail Filtering Language",
              RFC 3028, January 2001.

   [RFC3834]  Moore, K., "Recommendations for Automatic Responses to
              Electronic Mail", RFC 3834, August 2004.

8.2  Informative References

   [RFC2142]  Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
              FUNCTIONS", RFC 2142, May 1997.


Authors' Addresses

   Tim Showalter
   ??

   Email: tjs@psaux.com


   Ned Freed
   Sun Microsystems

   Phone: +1 909 457 4293
   Email: ned.freed@mrochek.com

Appendix A.  Acknowledgements

   This extension is obviously inspired by Eric Allman's vacation
   program under Unix.  The author owes a great deal to Carnegie Mellon
   University, Cyrus Daboo, Lawrence Greenfield, and many others whose
   names have been lost during the inexcusably long gestation period of
   this document.





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   Internet Society.




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