DNSBL stands for Domain Name System-based Blackhole List. A DNSBL lists IP addresses, usually those that have been observed by the list operator to send junk e-mails, that are used by applications to decrease the delivery of junk e-mails. These lists are developed by third-party entities and are not supported or maintained by pair Networks. However, we give you the option of using particular DNSBLs, which may reduce the amount of junk e-mails you receive.

It really depends on your intentions. Some DNS blacklists are more effective than the others, but may have a higher false positive rate. To help your selection, we publish DNS blacklist usage and effectiveness statistics on our website which includes user comments. You can also ask for other users's opinion on the ORF newsgroups.

The DNSBL (DNS BLacklist) databases collect IP addresses of spammer servers, open relay mail servers, open proxies, spam-supporting ISPs, dial-up lines, etc. that are known or possible spam sources. As their name implies, DNS blacklist databases can be queried using DNS lookups. Often they are also referred as RBL's (Realtime BLackhole) or ip4r databases.

We can't really provide documentation for every DNSBL there is, mainly because the policies and procedures of those DNSBLs may change from time to time. So, this section will give links to the relevant documentation for some DNSBLs. Tor is an effort by the Electronic Frontier Foundation to provide completely anonymised Internet use. As a result the possibility for abuse of poorly-designed protocols like IRC is immense. There exists a Tor DNSBL with instructions for configuring in BOPM.

DNS-based blacklists are very dangerous things. The organization running the list is giving its guarantee that all of the hosts it contains are "bad" in whatever way. It is of utmost importance that the criteria for being listed are well defined. It is preferable if the list is maintained in an automatic fashion to avoid any accusations of people being added or removed for personal reasons. All of that is quite easy with something as clear-cut as insecure proxies.