E-mail has become a critical marketing tool for small businesses. By giving smaller firms the ability to market as effectively as larger ones with no incremental costs for increasing the number of e-mails, email has truly been one of the boons of the Internet age.

Unfortunately, there’s also no additional cost for spammers, so the amount of unwanted e-mail is escalating sharply, giving rise to "blacklists" that companies are increasingly using to help spot and automatically block unwanted e-mails. E-mail hosting services such as Yahoo! and AOL have their own blacklists. There are also blacklists operated by smaller organizations.

While the blacklists are designed to thwart spammers, sometimes they thwart the legitimate e-mail marketing efforts of legitimate small businesses. Joel Smith, chief technology officer for AppRiver LLC, located in Gulf Breeze, Florida., says that valid businesses getting blacklisted is one of the top support issue for his spam-and-virus filtering firm.

Although it's best to try and stay off all blacklists, a small business may not have the resources to monitor all of them. Most experts agree that the ones to be most concerned with are Spamhaus and SpamCop.

There are different procedures for getting off different blacklists. Some require only a phone call or e-mail. Others have very specific procedures. Follow those procedures to the letter, Sullivan recommends. If there are five steps, follow all five, not just four. Failing to do so will keep you on the blacklist. “They’re very rigid about the procedures,” Sullivan says.