relay_recipient_maps doens't work

Hi list,

I want to use relay_recipient_maps on a postfix 2.5.1 relay server but  
it doens't appear to be doing anything. I want to accept mail for  
existing users only but it accepts mail for all users.

this is postconf -n

append_at_myorigin = no
append_dot_mydomain = no
biff = no
config_directory = /etc/postfix
content_filter = smtp-amavis:[127.0.0.1]:10024
inet_interfaces = all
local_recipient_maps =
mailbox_size_limit = 0
message_size_limit = 25000000
mydestination =
myhostname = server.domain.com
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
myorigin = domain.com
readme_directory = no
recipient_delimiter = +
relay_domains = mysql:$config_directory/mysql_relay_domains_maps.cf
relay_recipient_maps = mysql:$config_directory/mysql_relay_maps.cf
smtp_host_lookup = native,dns
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
transport_maps = mysql:$config_directory/mysql_transport_maps.cf
unknown_address_reject_code = 450
unknown_local_recipient_reject_code = 450
virtual_alias_maps = mysql:$config_directory/mysql_virtual_alias_maps.cf

this is mysql_relay_maps.cf

user = username
password = secret
dbname = database
hosts = maildb
query = SELECT user_name FROM database WHERE user_name='%s'

the mysql connection works (or else mail would not be delivered at all)