2. Don't follow industry best practices for mailing lists.

Any newsletter you send should use confirmed opt-in (sometimes called closed-loop opt-in) to ensure that the person who signed up is the person to whom the e-mail will be sent. This is a biggie. If your newsletter doesn't follow this rule and you get onto a blacklist for any reason, you won't be removed from the list until the confirmed opt-in issue is addressed.

Make it easy to unsubscribe from a mailing list. Even when you do make it a one-click action, entirely too many people fail to unsubscribe and instead stab angrily at the This Is Spam button in their e-mail client. Big e-mail ISPs like Yahoo Mail won't block your newsletter for a single spam report, nor will they list you in an RBL because of one lazy newsletter recipient, but you don't want to get anywhere close to the line.

Another express ticket to the blacklists is to repurpose addresses. "Don't store a user's e-mail address for one reason and then send them bulk e-mail for a completely different reason," explains Richi Jennings, lead analyst, e-mail security practice for Ferris Research. For example, a hosted anti-spam service allegedly mailed its customers' technical contacts a marketing message. When customers signed up for the service, they provided a technical contact for messages about service outages, trouble-ticket updates, etc. "The technical contact has a clear expectation of the types of messages they'll receive, and that doesn't include marketing," says Jennings.

3. Let anyone use content-sharing features, willy-nilly.

Many sites (yes, including CIO.com) encourage readers to participate in some way. You might comment on an article (we writers do appreciate it, not that I'm hinting or anything), or e-mail the article link to a friend, or (with modern social networking tools) create your own page.

Those are great. But blog comments can generate comment spam, which points right back at your domain. Many sites' "e-mail this article" feature is malformed (for example, spoofing the "from" address), leading to bounce messages if not the land of blacklists. And so on.

Catherine Hampton Jefferson from SpamBouncer, explains, "If you're a news site, for example, and want to let people forward a news story to someone, you should restrict them to sending it to a small number of e-mail addresses. I'd also check the IP they're connecting from against the CBL and perhaps other carefully selected blocklists."

4. Use a dubious service provider.

It's astonishing how often companies choose an ISP or Web hosting service without doing due diligence. Before you sign up, find out how often the company was blacklisted in the last year. Discover if they're known to route hijacked network space, or if they have a history of spam/abuse support. (One recommended resource for this is SenderScore.)