I've put of a new DNS list with a twist. You can look it up by host
name. And using it from Exim is very easy. Feel free to use it.
White List
accept dnslists = hostkarma.junkemailfilter.com=127.0.0.1/$sender_host_name
Black List
drop dnslists = hostkarma.junkemailfilter.com=127.0.0.2/$sender_host_name