skip spamd for outgoing mail

Hi,


I'm using vexim (last release) on a box which has some sites sending  
confirmation mails and newsletter.
I'd like to move spam detection using spamd from acl to  
transport_filter, to avoid the cpu load when sending a newsletter  
from a site.

Could you give me some indications on where I should insert the  
transport_filter rules in the exim4.conf ?

Thanks