1. Tool to Query RBL Servers This program is a very basic interface to DNS listings such as the RBL filter developed by Paul Vixie and the MAPS project. The basic idea of the filter is that when someone is blacklisted for email abuse of some sort, a new domain name is resolved of the form "2.0.0.127.domain.name.com", where 2.0.0.127 is the abusive IP address in reverse (for example, 2.0.0.127 would be the IP address 127.0.0.2), and "domain.name.com" is the base domain name of the filtering service (such as "blackholes.mail-abuse.org" for the MAPS project RBL filter). From Debian 3.0r0 APT