Sieve Email Filtering: Detecting Duplicate Deliveries
RFC 7352
Internet Engineering Task Force (IETF) S. Bosch
Request for Comments: 7352 September 2014
Category: Standards Track
ISSN: 2070-1721
Sieve Email Filtering: Detecting Duplicate Deliveries
Abstract
This document defines a new test command, "duplicate", for the Sieve
email filtering language. This test adds the ability to detect
duplications. The main application for this new test is handling
duplicate deliveries commonly caused by mailing list subscriptions or
redirected mail addresses. The detection is normally performed by
matching the message ID to an internal list of message IDs from
previously delivered messages. For more complex applications, the
"duplicate" test can also use the content of a specific header field
or other parts of the message.
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 in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7352.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 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.
Bosch Standards Track [Page 1]
RFC 7352 Sieve: Detecting Duplicate Deliveries September 2014
Table of Contents
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................3
3. Test "duplicate" ................................................3
3.1. Arguments ":header" and ":uniqueid" ........................5
3.2. Argument ":handle" .........................................7
3.3. Arguments ":seconds" and ":last" ...........................8
3.4. Interaction with Other Sieve Extensions ....................9
4. Sieve Capability Strings ........................................9
5. Examples ........................................................9
5.1. Example 1 ..................................................9
5.2. Example 2 .................................................10
5.3. Example 3 .................................................11
5.4. Example 4 .................................................12
6. Security Considerations ........................................12
7. IANA Considerations ............................................13
8. Acknowledgements ...............................................14
9. References .....................................................14
9.1. Normative References ......................................14
9.2. Informative References ....................................15
1. Introduction
This document specifies an extension to the Sieve filtering language
defined by RFC 5228 [SIEVE]. It adds a test to track whether or not
a text string was seen before by the delivery agent in an earlier
execution of the Sieve script. This can be used to detect and handle
duplicate message deliveries.
Duplicate deliveries are a common side effect of being subscribed to
a mailing list. For example, if a member of the list decides to
reply to both the user and the mailing list itself, the user will
often get one copy of the message directly and another through the
mailing list. Also, if someone crossposts over several mailing lists
to which the user is subscribed, the user will likely receive a copy
from each of those lists. In another scenario, the user has several
redirected mail addresses all pointing to his main mail account. If
one of the user's contacts sends the message to more than one of
those addresses, the user will likely receive more than a single
copy. Using the "duplicate" extension, users have the means to
detect and handle such duplicates (e.g., by discarding them, marking
them as "seen", or putting them in a special folder).
Bosch Standards Track [Page 2]
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