[Dovecot] Filtering spam in an offlineimap + dovecot setup

[Alan Schmitt]

Hello,

To easily access my mail both offline on my computer and on my phone, I
am synchronizing a local copy on my computer using offlineimap. As the
spam filtering options provided on the server are not sufficient, I am
now looking into client-side spam filtering.

My current setup is as follows. Mail is synchronized using offlineimap,
and delivered to a local dovecot server:

--8<---------------cut here---------------start------------->8---
[Repository LocalIMAP]
type = IMAP
preauthtunnel = /usr/local/Cellar/dovecot/2.2.10/libexec/dovecot/imap -c ~/.dovecotzimbra.rc
--8<---------------cut here---------------end--------------->8---

The configuration of the local server is simply:

--8<---------------cut here---------------start------------->8---
protocols = imap
mail_location = maildir:~/.Maildir/zimbra:INBOX=~/.Maildir/zimbra/.INBOX
--8<---------------cut here---------------end--------------->8---

I then read my mail using gnus, and index it using notmuch.

A suggestion I've been considering is use the pigeonhole sieve
extprograms plugin
(http://wiki2.dovecot.org/Pigeonhole/Sieve/Plugins/Extprograms) to call
the spam filter (I've been looking at dspam at the moment). However, I
could not find how to configure the use of sieves in the context of
offlineimap. Hence my questions:

Is it possible to use dovecot sieves in such a setting? Is there a howto
that explains how to do it?

Should I try to do things in a different way? (I'm ready to change my
setup, as long as I can keep an offline copy of my email in sync with
a server copy.)

Thanks a lot for any suggestion,

Alan

PS: I used to use SpamSieve (http://c-command.com/spamsieve/) on a Mac
Mini that was running continuously as a spam filter drone. This machine
has been retired and I'm basically looking for leaner ways to do a
similar thing.