This is a general question, mainly because I
don't know what to search for to do what I want...

I have a dedicated web server running Fedora 5
that has a exim mail server running, as well as
a mysql 4.1.22 database. Basically, I would like
to have a daemon running that logs all incoming
and outgoing e-mail into the database. Well, not
all e-mail, just e-mails from previous or current
clients. The flow of this program would be something
like this:

- Detect that an e-mail has been received.
- Check the database to see if a client exists with
that e-mail, and if there is one, then insert a row
into the database containing the message of the text
and other info.

Any ideas? Ideally, there is some event that I can
catch (i.e., when an e-mail is sent or received through
the mail server) that will let me run an external program
when said event happens. For example:

onReceiveEmail || onSentEmail: php /my/email/handing/script.php

Is this possible? Any information would be useful.
Thanks in advance,

-Jason