[Exim] Exim and Sieve rules

Hello all,

We are looking at building a mail platform using Exim 4.3 + Amavis +
SpamAssassin + Courier. We are also *very* keen on Horde/IMP and the support
it provides for server-side mail filters... However, it does not provide
support for maildrop yet and supports only procmail and sieve rules. I prefer
sieve rules to maildrop since it is an RFC standard etc. and easy to manage.
We have built a prototype mail system with everything we need and it is working
perfectly... the only problem is that we are using Cyrus+timsieved for the mail
store. There are a number of reasons why we prefer Courier (e.g. NFS safe,
Maildir format etc.) - however, we are stuggling to get Sieve support working
with Courier. So, we turned to the Sieve support in Exim instead - however we
are struggling to get it working. We have setup a router as so:

driver = redirect
check_local_user
allow_filter
file = $home/.forward
no_verify

The $home/.forward is just for testing... This works okay for redirects, but we
are stuggling to understand how we can get Exim to 'forward and keep' a
message. What file_transport should we use to deliver the message to the
mailbox? I also understand that Exim sieves don't support 'reject' etc.

Can anybody give me a few pointers on how I can achieve sieve rules with an Exim
+ Courier combination?

Cheers,
Ray