Black List Lookup:
Open Relay Database (ORDB) – http://www.ordb.org/
A validated database of mail servers that permit third-party relay. Also in Francais, Nederlands and Dansk.

Spamhaus Block List (SBL) – http://www.spamhaus.org/sbl/
All IPs on the SBL belong to known spammers, spam gangs, or spam support services. The SBL includes IPs from both the ROKSO database and IPs of spam services listed in the Spamhaus database.

Mail Abuse Prevention System – http://mail-abuse.org/
MAPS aims to defend the Internet from spammers by educating ISPs and providing real time blocking lists of known spam sources.

Composite Blocking List (CBL) – http://cbl.abuseat.org/
The CBL is a DNSBL which takes its source data from very large spamtraps, and lists IPs of open proxies and worms/viruses.

MAPS Realtime Blackhole List (RBL) – http://mail-abuse.org/rbl/
Lists email sites which have refused to limit their relaying, leaving the potential for their use as spam gateways.

The Spamhaus Project Register of Known Spam Operations (ROKSO) – http://www.spamhaus.org/rokso/
The Spamhaus Project’s Register Of Known Spam Operations (ROKSO) Database. ROKSO collates evidence on known hard-line spam outfits that have been thrown off Internet Service Providers over three times.

rfc-ignorant.org – http://www.rfc-ignorant.org/
The home for domains who don’t play by the rules. A number of lists (at present “dsn”, “abuse”, “postmaster”, “whois” and “ipwhois”) which contain domains or IP networks whose administrators choose not to obey the RFC’s, the building block “rules” of the net.

Distributed Server Boycott List (DSBL.org) – http://www.dsbl.org/
This list contains email servers which are non-secure and potentially servers with dumb and/or malicious users. It is purely composed of data DSBL receives; DSBL should never send out data by itself.

Spam Prevention Early Warning System (SPEWS) – http://www.spews.org/
SPEWS maintains a list of known spam sources and spam friendly hosts so that e-mail can be rejected from these problem sites.

MAPS Dial-up User List (DUL) – http://mail-abuse.org/dul/
An IP blacklist of dialup-using “stealth” spammers and email trespassers.

Spam & Open Relay Blocking System (SORBS) – http://www.dnsbl.sorbs.net/
Lists Open Relays and Open Proxies (Open HTTP Proxy Servers and Open SOCKS Proxy Servers). SORBS only scans a host when it attempts to send mail to one of the feeder servers.

Spambag.org – http://www.spambag.org/
Personal (DNSBL) list of abusive networks that the author blocks from sending mail or accessing his web servers.

The Abusive Hosts Blocking List (AHBL) – http://www.ahbl.org
Publishes a list of known abusive hosts (open relays, open proxies, spam sources, DoS drones, and more) in various forms including a DNSbl.

SpamCop – Blocking List Information – http://spamcop.net/bl.shtml
This list contains IP addresses which have been reported to SpamCop as carriers of spam (source of e-mail or verified, open relay). Some of these reports now come from spamtraps (email addresses used strictly to receive spam).

bl.csma.biz – Spam Blacklist – http://bl.csma.biz/
As a public service, McFadden Associates maintains a free DNSBL blacklist. Anyone sending SPAM into their mail filters is automatically added for a period of thirty days.

MAPS Relay Spam Stopper (RSS) – http://www.mail-abuse.com/services/mds_rss.html
The RSS is a list of email relays which have been used to send spam, for use in blocking spam by blocking mail which have gone through those sites.

Five Ten – Local Black Holes – http://www.five-ten-sg.com/blackhole.php
Blacklist that includes dialup equivalent ip addresses, individual spam sources, netblocks that refuse to remove spammers, bulk mailers that don’t require confirmed opt-in, output servers from multi-stage open relay chains and single stage open relays not listed on ORBZ.

Not Just Another BlackList (NJABL.ORG) – http://njabl.org/
Spam blocking blacklist of open relays, dial-ups, and direct spam sources.

The South Korea Blocking List – http://korea.services.net/
Blocking list to filter out Korean spam.

MailPolice RHS-BL – http://rhs.mailpolice.com
RHS-style lists of domains which have sent spam to MailPolice customers. Currently divided into two lists, bulk senders – domains associated with bulk mail – and pornography – domains associated with sending and hosting pornographic content.

AntiSpam DNSBL – http://antispam.or.id
Identifies spam sources – whether intentional or not – at the time they are sending spam. Not before and not after.

ip4r (DNSBL-style) DNS lookups – http://www.declude.com/junkmail/support/ip4r.htm
List, in table form, of blacklists. Includes table with the name of the blacklists, their lookup domains, the IP that is returned in case of a match and a description.

Better Ethics Online – http://actionsites.com/beo/
Publishes black list of spammers and seeks to promote online ethics.

Spamikaze – http://spamikaze.nl.linux.org/
Automated spam blocklist system, designed to block spam at the SMTP level.

Blacklists Compared – http://www.sdsc.edu/~jeff/spam/Blacklists_Compared.html
Weekly reports of DNS blacklists lookups of IP addresses (and reverse DNS lookups) that made SMTP connections to the San Diego Supercomputer Center on that week. Useful for getting a grasp of the size of the various blacklists. Maintained by Jeff Makey.

Clueless Mailers – http://www.cluelessmailers.org/
Offers background information on the worst of the new Internet abusers.

Drbcheck: Dr. Jorgen Mash’s DNS Database List Checker – http://moensted.dk/spam/
Lists all DNSbl’s (RBL’s) and enables users to make a query against all the lists.

Spamware Vendor List – http://www.spamsites.org
List of live spamware sites and related links.

Blacklist of Internet Advertisers – http://www.non.com/news.answers/advertisers-blacklist.html
To curb inappropriate advertising on usenet newsgroups and via junk e-mail.

UCE Protect Network – http://www.uceprotect.net/en/
Attempt to generate a free realtime black list of spammer IP numbers.

Whois-Details for Blacklisted Spam Domains – http://www.joewein.de/sw/bl-log.htm
List of domains that have been advertised via spam, with name server, registration date, registrant. This list is updated daily.

Chinese and Korean Net Blocks – http://www.okean.com/asianspamblocks.html
Lists IP blocks of China and Korea for those who want to avoid asian spam.

Blackholes.us – http://blackholes.us/
Publishing a variety of DNS blocklists including entire countries and ISP’s.

Blitzed IRC Network (OPM.BLITZED.ORG) – http://www.blitzed.org/proxy/
A dnsbl of open proxies (HTTP, Socks and wingate), populated by IRC connection scanners and spamtraps.

Electric Eye Ultimate Banned List – http://electriceye.net/banned
A manually updated and verified online database of spammers. Provides email address and domain blocklist.

Spamerang – http://www.spamerang.net
A call for all internet users to turn the spammers’ own email addresses into spam bait.

Spambag of the Month – http://www.spambag.net/
Makes examples of people who feel the need to send unsolicited emails. Sample emails and follow-up information.

Spam Support Permanent Blocklist – http://sspbl.tripod.com/
A permanent blocklist of spam supporting web hosts and ISPs.