[exim] exim and sieve filters

Hi,

We currently have a setup where exim delivers to Maildir, and each user
has a .forward with an exim filter. Users access their mail using
Thunderbird via IMAP (using dovecot). So far, everything is working fine.

Now I'm looking for a way to automatically label all new mails in one
specific account so they appear as 'to do' in Thunderbird (I can't do
that in Thunderbird itself since it's a shared account that's used from
different client machines). As far as I can see, that cannot be done in
an exim filter, but it can be done in a sieve filter using addflag
"$label4".

I tried that, but that doesn't work in the current setup; the log says

appendfile: file or directory name "inbox" is not absolute

The docs say that the name inbox must be handled for Sieve filters, and
show a way to set the file setting in the appendfile transport.

So I think I need to set the directory setting (not file, since we're
using Maildir) in the appendfile transport in a way that handles the
Sieve name 'inbox' in a way suitable for Maildir, and also still
supports the exim filters of all the other accounts (though I could
convert all those to Sieve filters if there's no other way).

I thought that should be a relatively common setup, but I can't find any
information on it. Can someone give me some pointers on how to do this?

(we're using exim 4.63-17 on Debian etch)

Best regards,
Roel

--
The saddest aspect of life right now is that science gathers knowledge
faster than society gathers wisdom.
-- Isaac Asimov

Roel Schroeven