Pigeonhole Sieve: Duplicate Extension
=====================================

The *duplicate* extension RFC 7353 [http://tools.ietf.org/html/rfc7352] adds a
new test command called 'duplicate' to the Sieve 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.

Previously, this extension was Dovecot-specific and available under the name
'vnd.dovecot.duplicate'. Specification for old version available here
[http://hg.rename-it.nl/dovecot-2.1-pigeonhole/raw-file/tip/doc/rfc/spec-bosch-sieve-duplicate.txt].
That implementation differs significantly from what is now published as RFC
7353 [http://tools.ietf.org/html/rfc7352], but the original extension is still
supported for backwards compatibility.

Configuration
-------------

The *duplicate* extension is available by default. The *duplicate* extension
has its own specific settings. The following settings are available (default
values are indicated):

sieve_duplicate_default_period = 14d :

sieve_duplicate_max_period = 7d :
  These options respectively specify the default and the maximum value for the
  period after which tracked values are purged from the duplicate tracking
  database. The period is specified in s(econds), unless followed by a d(ay),
  h(our) or m(inute) specifier character.

Example
-------

---%<-------------------------------------------------------------------------
plugin {
  sieve = ~/.dovecot.sieve

  sieve_duplicate_default_period = 1h
  sieve_duplicate_max_period = 1d
}
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2017-10-10 04:42)