from the Opt-in Email Marketing Resource Center

Blacklists are lists of either IP addresses or domain names that have been accused of sending unsolicited commercial email. They are subscribed to by many Internet Service Providers (ISPs). If a website or IP address is added to a blacklist and the ISP that site is attempting to send email to subscribes to the blacklist, the email will likely not get through to the intended recipient.

While blacklists have been helpful in filtering out and reducing spam, many innocent sites are added blacklists. Often, business owners who send out opt-in, or permission-based, newsletters are reported by one of their subscribers who simply forgot that they ever subscribed. Most blacklists are automated and blacklist first and ask questions later.

Here is an excerpt from a whitepaper on blacklists that explains the problem of blacklists that permission-based businesses face:

Blacklists operate on a reporting system, in which an individual can forward an email they consider to be spam to the list operator, who then adds that person or entity to the list of known senders of unsolicited commercial email. Unfortunately, the operators of these blacklists are not answerable to anyone and they run their operations with extreme prejudice against anyone who is attempting to earn revenue from electronic commerce. They require no proof that the offending email was actually unsolicited, they do not notify the business in question that they have been blacklisted, nor do they offer that person or entity an opportunity to defend themselves before they are placed on such a list. This is a situation that begs to be abused. There have been numerous instances in which online businesses have found themselves on such a blacklist for reasons that range from the user who subscribes to a newsletter and then forgets that they did, to a competitor attempting to thin the field, to the malicious promptings of a personal grudge. - Making Room for the Business Use of Email p. 5

In order to check to see if your website is on a blacklist, simply go to www.openrbl.org and type in your domain name. The site will do a quick check against its database of 31 major blacklists and within seconds tell you which, if any, that your website(s) are on. Another good tool that will allow you to check to see if you are on blacklists can be found at www.senderbase.org.

Getting off a Blacklist

If you get on a blacklist, it is often difficult to get off. You can try to visit the web site of the blacklist you are on and look for removal procedures. Some blacklists have procedures for removal, while other lists are permanent.

Listing of Major Blacklists

? SPAMHAUS abuse.net/sbl.phtml
? SPAMCOP bl.spamcop.net
? SPEWS spews.org (Spam Prevention Early Warning System)
? SPEWS relays.osirusoft.com
? MAPS RBL http://mail-abuse.org/rbl/
? MAILABUSE blackholes.mail-abuse.org
? DNSBL spam.dnsrbl.net
? BLARS block.blars.org
? BLACKHOLES blackhole.compu.net
? EASYNET blackholes.easynet.nl
? FIVETEN blackholes.five-ten-sg.com
? SPAMGUARD spamguard.leadmon.net
? SORBS dnsbl.sorbs.net
? SPAMBAG blacklist.spambag.org
? BLITZED opm.blitzed.org
? XBL xbl.selwerd.cx
? DNSBL in.dnsbl.org
? MAILPOLICE bulk.rhs.mailpolice.com
? SPAMSITES spamsites.org
? DSBL dsbl.org
? NJABL njabl.org