[exim] Newbie with local_user mysql lookup

Hello fellas,

    I am new to Exim and I am trying to set a couple of features with it
unsuccessfully. I am using Exim4 on a Debian system (exim4-heavy) with
Courier-IMAP and DSPAM. Everything seems to work just fine but the
local_user message delivery.

    Below is my router and the lookup I am trying to do. The problem is
that doesnt matter to what recipient I send email, it will always be
delivered despite of the lookup. What am I missing?

local_user:
debug_print = "R: local_user for $local_part@$domain"
driver = accept
domains = +local_domains
condition = lookup mysql{select id from passwd where id='$local_part@
$domain'}
transport = maildir_home
cannot_route_message = Unknown user




Thanks,

Mesquita