[exim] Log to sql

Hi

I thought i should start to log the sender/resciver in all mails that
passes my mailserver to minimize falsepositives in spam handling, ie
mails that are sent from outside systems and replied to should be always
be considered ham, regardless if their mailserver gets blacklisted or
something like that,
So i have tried to add sql lines in different places in transport/router
config but, it doesn't behaves as i thought it would. the sql command is
run even if message is frozen by acl, or sometimes run several times for
each mail, so i thought somebody here might help me out, where should i
add such a line so it would only be run once and only where mail is
actually written to users maildir