[Exim] receiver_verify problem

hi,
i set the receiver_verify option to get rid of those bounce-mails my system
tries to deliver to non-existent spammers.

sadly, it does not work. my system still accepts any local_part, even if it is
non-existent. i searched the archives, the faq and the book but had no luck
with this.

do i have do give some additional options to my directors to make this work?
my first director looks like this:

spamcheck_director:
condition = "${if eq {$received_protocol}{spam-scanned} {0}{1}}"
driver = smartuser
transport = spamcheck
verify = yes

exim version is 3.35 (debian woody).

thanks