[exim] Internal RBL

Hi Guys,

Has anyone implemented an Internal RBL to automatically block and
unblock spamming IPs within their network?
I am looking at a scenario like the way Greylisting works -
temporarily blocks sender IPs and maintains a database that updates
when it temporarily whitelists the IP which then bypasses greylist
checks.

In my case, i would require a solution in exim that would do the following;

1. If a sending IP has a spam score in amavis > 20, more than x times,
then it should be dumped in a database which exim will use to
temporarily block the IP
2. If the sending IP has not attempted to spam again in x days, then
the entry is expired in the database
3. If the sending IP attempts to spam again while an entry for the IP
is in the database, then the entry should be extended in the database
for another x days.

Any ideas appreciated.

Dru.