[Exim] Getting lists of users from odd databases?

We are finally going down the route of an all-staff and an all-student
email list (the acceptability of this can be argued elsewhere - I am
"argued out" :-). We currently have a mojordomo server that we hope to
replace with mailman over the summer. the lists need to be working (for
trials at least) before the Summer vac.

Using Majordomo is an option but we have had a couple of experiences where
users have been able to send to the list despite the config denying them.
This happening to a staff list of 2000 or a student list of 12000 is scary!
Also, as we are hopefully dropping majordomo soon it seems pointless
spending time on this.

We have an admin database that manages all of our accounts and holds info
on the status of the user. Ideally, we would like to get exim to send to
a list of users that it obtains from this database. As the format is
non-standard (to say the least!) we would need to create a binary that
returns a list of users from the db (no probs) but how would I then
get that info into exim for the mail to be sent? Moving the db backend
to something standard is not an option at the moment.

Initial thoughts (these maybe impossible or just plain stupid - please
comment!) are:

- Setup a mail service on a nonstandard port that uses some sort of smtp
auth to prevent anyone poking email at it. There will be a very limited
set of people who will be able to send to the list.

- email to all-students would cause exim to run our binary to obtain a list
addrs and then to send the email on to them with the email appearing to
be from a announce@??? addr (say)

- email to announce@??? to be rejected with a standard response telling
the sender that the list is announce only.

An improvement on this would be to allow email to all-students-1@???
to result in our binary being run with the suffix being passed to it to
allow the search to be restricted in someway ( -1 meaning year 1, -2 meaning
year 2 students for example). This would allow a simple way to limit the
recipients and would hopefully reduce the number of students complaining
that the info that we are spamming them with is not applicable to their
year/course/whatever.

Does this sound do-able? Am I mad for thinking this? Is anyone doing
similar (and if so, can I have a look at your config please?!). I could
just create mail lists with the addrs in but using the database seems to
be an ideal way as it will always be up to date and will need no extra
admin to manage.

Suggestions?

Darren
--
Senior Computing Officer
University of Kent