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rfc:rfc3598

Network Working Group K. Murchison Request for Comments: 3598 Oceana Matrix Ltd. Category: Standards Track September 2003

           Sieve Email Filtering -- Subaddress Extension

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

 On email systems that allow for "subaddressing" or "detailed
 addressing" (e.g., "ken+sieve@example.org"), it is sometimes
 desirable to make comparisons against these sub-parts of addresses.
 This document defines an extension to the Sieve mail filtering
 language that allows users to compare against the user and detail
 parts of an address.

Table of Contents

 1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Capability Identifier . . . . . . . . . . . . . . . . . . . .   2
 3.  Subaddress Comparisons. . . . . . . . . . . . . . . . . . . .   2
 4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
 5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
 6.  Normative References. . . . . . . . . . . . . . . . . . . . .   4
 7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
 8.  Intellectual Property Statement . . . . . . . . . . . . . . .   5
 9.  Author's Address. . . . . . . . . . . . . . . . . . . . . . .   5
 10. Full Copyright Statement. . . . . . . . . . . . . . . . . . .   6

Murchison Standards Track [Page 1] RFC 3598 Sieve Email Filtering September 2003

1. Introduction

 Subaddressing is the practice of appending some "detail" information
 to the local-part of an [IMAIL] address to indicate that the message
 should be delivered to the mailbox specified by the "detail"
 information.  The "detail" information is prefixed with a special
 "separator character" (typically "+") which forms the boundary
 between the "user" (original local-part) and the "detail" sub-parts
 of the address, much like the "@" character forms the boundary
 between the local-part and domain.
 Typical uses of subaddressing might be:
  1. A message addressed to "ken+sieve@example.org" is delivered into a

mailbox called "sieve" belonging to the user "ken".

  1. A message addressed to "5551212#123@example.org" is delivered to

the voice mailbox number "123" at phone number "5551212".

 This document describes an extension to the Sieve language defined by
 [SIEVE] for comparing against the "user" and "detail" sub-parts of an
 address.
 Conventions for notations are as in [SIEVE] section 1.1, including
 use of [KEYWORDS].

2. Capability Identifier

 The capability string associated with the extension defined in this
 document is "subaddress".

3. Subaddress Comparisons

 Commands that act exclusively on addresses may take the optional
 tagged arguments ":user"  and ":detail" to specify what sub-part of
 the local-part of the address will be acted upon.
 NOTE: In most cases, the envelope "to" address is the preferred
 address to examine for subaddress information when the desire is to
 sort messages based on how they were addressed so as to get to a
 specific recipient.  The envelope address is, after all, the reason a
 given message is being processed by a given sieve script for a given
 user.  This is particularly true when mailing lists, aliases, and
 "virtual domains" are involved since the envelope may be the only
 source of detail information for the specific recipient.

Murchison Standards Track [Page 2] RFC 3598 Sieve Email Filtering September 2003

 The ":user" argument specifies that sub-part of the local-part which
 lies to the left of the separator character (e.g., "ken" in
 "ken+sieve@example.org").  If no separator character exists, then
 ":user" specifies the entire left-side of the address (equivalent to
 ":localpart").
 The ":detail" argument specifies that sub-part of the local-part
 which lies to the right of the separator character (e.g., "sieve" in
 "ken+sieve@example.org").  If no separator character exists, the test
 evaluates to false.  If nothing lies to the right of the separator
 character, then ":detail" ":is" the null key ("").  Otherwise, the
 ":detail" sub-part contains the null key.
 Implementations MUST make sure that the separator character matches
 that which is used and/or allowed by the encompassing mail system,
 otherwise unexpected results might occur.  Implementations SHOULD
 allow the separator character to be configurable so that they may be
 used with a variety of mail systems.  Note that the mechanisms used
 to define and/or query the separator character used by the mail
 system are outside the scope of this document.
 The ":user" and ":detail" address parts are subject to the same rules
 and restrictions as the standard address parts defined in [SIEVE].
 For convenience, the "ADDRESS-PART" syntax element defined in [SIEVE]
 is augmented here as follows:
    ADDRESS-PART  =/  ":user" / ":detail"
 A diagram showing the ADDRESS-PARTs of a email address utilizing a
 separator character of '+' is shown below:
     :user "+" :detail  "@" :domain
    `-----------------'
        :local-part
 Example:
 require "subaddress";
 # File mailing list messages (subscribed as "ken+mta-filters").
 if envelope :detail "to" "mta-filters" {
   fileinto "inbox.ietf-mta-filters";
 }
 # If a message is not to me (ignoring +detail), junk it.
 if not allof (address :user ["to", "cc", "bcc"] "ken",
      address :domain ["to", "cc", "bcc"] "example.org") {
   discard;

Murchison Standards Track [Page 3] RFC 3598 Sieve Email Filtering September 2003

 }
 # Redirect all mail sent to +foo.
 if envelope :detail ["to", "cc", "bcc"] "foo" {
   redirect "ken@example.edu";
 }

4. Security Considerations

 Security considerations are discussed in [SIEVE].  It is believed
 that this extension does not introduce any additional security
 concerns.

5. 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 extension
 Capability name: subaddress
 Capability keyword: subaddress
 Capability arguments: N/A
 Standards Track/RFC 3598
 Person and email address to contact for further information:
 Kenneth Murchison
 ken@oceana.com
 This information has been added to the list of sieve extensions given
 on http://www.iana.org/assignments/sieve-extensions.

6. Normative References

 [IMAIL]    Resnick, P., Ed., "Internet Message Format", RFC 2822,
            April 2001.
 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [SIEVE]    Showalter, T., "Sieve: A Mail Filtering Language", RFC
            3028, January 2001.

Murchison Standards Track [Page 4] RFC 3598 Sieve Email Filtering September 2003

7. Acknowledgments

 Thanks to Tim Showalter, Alexey Melnikov, Michael Salmon, Randall
 Gellens, Philip Guenther and Jutta Degener for their help with this
 document.

8. Intellectual Property Statement

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

9. Author's Address

 Kenneth Murchison
 Oceana Matrix Ltd.
 21 Princeton Place
 Orchard Park, NY 14127
 EMail: ken@oceana.com

Murchison Standards Track [Page 5] RFC 3598 Sieve Email Filtering September 2003

10. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assignees.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Murchison Standards Track [Page 6]

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