Hi!
Can't you do zone transfers? Then you can do away with the subscriber_key thing and have DNS resolve locally for spamhaus.org and not have to query their DNS servers.
They sell datafeed and they sell queries, we bought queries. I do not believe they would think kindly on my trying a zone transfer. I'm just happy we got a paid subscription. It's the best support I can provide Spamhaus to keep them in business.
I wish you good luck doing a zone transfer on a rbldnsd server, its not implemented so its not an available option.
Bye, raymond.
