[exim] system filter

Hi all i want to move spam msg to custom folder

i use this options in exim configure and bogofilter to mark msg as spam . But nothing is happens

2005-09-11 01:04:44 1EEDSm-000JtB-C8 original recipients ignored (system filter)
2005-09-11 01:04:44 1EEDSm-000JtB-C8 == /var/db/spam <system-filter> T=address_file defer (-4): mailbox /var/db/spam is not a regular file

#system_filter = /usr/local/etc/exim/spam_filter
#system_filter_user = exim
#system_filter_group = nobody
#system_filter_directory_transport = /var/db/spam
#system_filter_file_transport = address_file

spam_filter
# Exim filter
if not first_delivery then
finish
endif

if error_message then
finish
endif

if $h_subject: contains  "***SPAM***"
 then
     save /var/db/spam

        endif

this is msg header after bogofilter

From: "Byron Kendall" <zsufvwd@???>
Subject: ***SPAM*** Huge Penis 9Ie

X-SpamFilter: Yes
X-SpamFiltered: Spam, tests=spamfilter on mailserver.sss.com, spamicity=1.000000, version=0.96.0