[Dovecot] Odd Feature Request - RBL blacklist lookup to prevent authentication

[Marc Perkel]

I would like to have a list of IPs (hacker list) that I can do a lookup 
on so that if anyone tries to authenticate to dovecot they always fail 
if they are on my list.

I have the list - and the list is available as a DNS blacklist.
I'd like to have it work with both local IP lists or RBL lookup.

The idea is so hackers from known IP addresses never succeed.

If Dovecot provides the feature I have about 1/2 million IP addresses of 
known current hackers to block.

Anyone else interested in this?