[exim] Filterung does not work

Hi there,

I suppose there is a little mistake in my filter file, but I don't get
it. Please help ;-)

The .forward file is:
-----------
# Exim filter

logfile $home/filter.log

logwrite "$message_id Checking ..."
if
$h_X-Spam-Flag: CONTAINS "Yes"
then
logwrite "$message_id is spam!"
save Maildir/.Trash/
finish
endif
logwrite "$message_id is not spam."
------------

I sent a test mail to myself using
$ mail -a "X-Spam-Flag: YES" me@address

I can see the X-Spam-Flag in my MUA, so it is definitely there. But
filter.log says:

------------
1M6iPs-0007u2-Cg Checking ...
1M6iPs-0007u2-Cg is not spam.
------------

And of course, the message was delivered to Maildir/ instead of
Maildir/.Trash/.

Thanks for your help.
Peter