[Exim] exim4, ldap, courier, debian

Hi, I am looking for a snippet to add to /etc/exim4/conf.d for a local
ldap lookup and delivery to a local imap store using courier-imap.

The goal is to have about 300 virtual users stored in a ldap directory,
from which exim4 will lookup and deliver to an imap store.

If anyone can point me in the right direction that would be great.