[Exim] SQL POP before SMTP method?

Here's an added feature I would like to add to my exim setup.

I would like to make an SQL-based POP before SMTP method, allowing users who
can't SMTP AUTH by other normal means, to be able to login through POP before
sending email out to anywhere.

I haven't a clue how to start this idea, but I'm guessing it's somehow
ACL-based in exim4?

I have a table, users, based on this layout, with only the relevant
information needed for this scheme to work:

  userid  |     last_login
----------+---------------------
 user1    | 2002-10-24 11:15:54
 user2    | 2002-10-23 09:35:51
 user3    | 1979-11-03 22:05:58
 user4    | 2002-10-24 11:47:11
 user5    | 2002-10-24 11:50:21

This is a PostgreSQL table, last_login using timestamp type field. I'm wanting
to allow users to send email out based on if their time is 5-minutes from the
last login.
Basically I have the WHERE clause to use, for that:

SELECT userid FROM users WHERE userid = ???? AND last_login > (now() - '5
minutes'::INTERVAL)::datetime;

But, I don't know how to get userid for the WHERE clause, or how to implement
this to work in exim4's ACLs.


--
Eric Renfro
Myrddin Computers & Designs - CEO/President
Sales: sales@???
Fax: (775) 243-4535