Do you feel that the DNSBL resolvers are too slow for your requests? In cases where this happens, you might want to apply for an own DNS slave server. You can do this by sending a mail to firstname.lastname@example.org – you can also send a mail if you would like to contribute with more slave servers to extend the reachability of the services. If you think the service is worth donating to, so that it can be extended furthermore, take a look here.
The current DNS servers are located in following countries: