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Re: [Dovecot] duplicates with multiple To/CC and sieve redirect copy Stephan Bosch Wed Feb 22 18:00:14 2012

On 2/22/2012 12:15 AM, Adam Szpakowski wrote:
On 22.02.2012 00:09, Timo Sirainen wrote:
Well, it would be possible to build a doveadm script that deletes the duplicates after delivery, but currently there's no implementation to avoid delivering duplicate Message-IDs in the first place.

I don't really like such a Message-ID-based deduplication feature enabled by default, but something like this could be nice:

fileinto :copy :x-deduplicate "boss";

Anyway, probably not going to be implemented anytime soon.
Maybe there is a way to use a procmail with something like this:

:0 Wh: msgid.lock
| formail -D 8192 .msgid.cache

But is there a safe way to use it together with sieve? Using Pigeonhole Sieve Pipe Plugin?


There are a few options:

* You can use Procmail as primary delivery agent and invoke dovecot-lda/sieve from within Procmail once Procmail has determined that it is not a duplicate.

* Invoke procmail from Sieve using the pipe extension (i.e. the other way around). This has the disadvantage that Procmail will have to take care of final delivery, meaning the Dovecot indexes are not updated.

* For Pigeonhole v0.3 there is the possibility to "filter" the message through Procmail using the sieve_extprograms plugin, but I haven't actually tested something like that.

* I've just created an alternative that implements something similar to the Procmail code you posted above, but from within Sieve itself. It is a custom language extension called vnd.dovecot.duplicate and it adds the "duplicate" test. This test keeps track of which Message-IDs it has seen before in earlier deliveries and yields a true result if the message was seen before, e.g.:

require "vnd.dovecot.duplicate";

if duplicate {
    discard;
}

Read the specification for details ("name" argument is not yet implemented):

http://hg.rename-it.nl/pigeonhole-0.3-sieve-duplicate/raw-file/4b1dbda4d3fc/doc/rfc/spec-bosch-sieve-duplicate.txt

The repository is at: http://hg.rename-it.nl/pigeonhole-0.3-sieve-duplicate

This plugin is only a few hours old, experimental, and largely untested, so test it thoroughly before considering to use this. Read the INSTALL file for compile and installation instructions.

Comments are welcome.

Regards,

Stephan.