[exim] pgsql lookup

Hi all

I'm using exim4-daemon-light (debian) for manage home mail without problems.

I'm deploying a web system (php+pgsql) and I'would like to integrate user
information between the web application and exim through postgresql. Looking
at debian cache, I saw that is possible to use pgsql for lookups using
exim4-daemon-heavy.

The documentation I had read (The Exim Specification - Version 4.4x) is hard
to understand for me becouse I haven't enough knowledge about exim. Is there
any other document about this feature? Could you please help me to configure
exim4 for sql lookups?

Any help would be appreciated.

Thanks in advance and sorry for my english.

--ejg