It's an Internet arms race that has spilled into all aspects of e-mail marketing: As quickly as ISPs come up with new ways to fight spam, spammers find new ways to deliver it. Surveys indicate that the biggest challenge facing sophisticated e-mail marketers is deliverability -- getting your opt-in messages through the spam filters and into your recipients' inboxes. But the problem isn't confined to huge brands like Lands' End or Wal-Mart. In fact, the challenge for smaller businesses, especially those unfamiliar with e-mail's thorny technical issues, can be formidable.

Deliverability is deceptively complex, and many marketers under-invest in the day-to-day processes that drive its successful execution. As a result, many do-it-yourselfers in particular suffer from exceedingly poor e-mail deliverability--sometimes without even knowing it.

Here are eight things you can do to avoid being caught in the crossfire of the spam wars:

  • Never send without permission. Never send commercial e-mail to people who haven't consented to receive it. It makes a poor brand impression, violates most ISP's terms of service, and almost guarantees deliverability problems. If your recipients aren't anticipating your e-mail, ISPs will go out of their way to make sure they don't get it.
  • Avoid spammy gimmicks. Your e-mail shouldn't resemble a bad Las Vegas lounge act. Spam filters seek patterns and irregularities often found in spam, so resist the temptation to spice up messages with all-caps, big fonts, weird punctuation, exclamation points, repeated phrases, or common advertising come-ons such as "free!" or "limited time offer!" It's also a good idea to screen your messages with a spam filter, such as SpamAssassin, to flag any potential content problems before you send.
  • Practice good list hygiene. Spammers' lists are littered with invalid and out-of-date information. One of the ways ISPs ferret them out is by watching for mailings with a high percentage of bad addresses. So, if an ISP "bounces" an address back to you as permanently undeliverable, scrub it from your list immediately. Strive for a hard bounce rate of no more than four to five percent. Anything above about seven percent is likely to impact your deliverability.
  • Don't ignore ISPs. E-mail marketers often don't realize they need to set up an mailbox in order for ISPs to be able to communicate information, such as bounce codes, back to a mailing's origin. If you don't have an appropriate mechanism for accepting an ISP's messages, you'll not only look like a spammer, but you'll have no way of knowing what ISPs are trying to tell you in order to address problems and ensure your mailings continue to get through.
  • Keep volume low. If you are sending marketing e-mail through your corporate server, you'll want to keep volume to a dull roar. Although the number varies wildly between ISPs, sending more than about 1,000 identical e-mails at a time is practically inviting an ISP to take a closer look and turn up the spam filters on what appears to be bulk e-mail pouring from an interpersonal e-mail server.
  • Protect your corporate IP address. Your Internet Protocol (IP) address is your unique "Internet address." Always send your marketing e-mail through a different IP address than the one you use for your corporate e-mail. That way, if you run into deliverability problems, you don't expose your corporate e-mail to risk. If the worst happens, and an ISP blocks your e-mail marketing IP address, you can still carry on with your necessary day-to-day business-related e-mail communications.
  • Implement authentication protocols. E-mail authentication protocols such as Sender Policy Framework, Sender ID and DomainKeys help ISPs ensure e-mail really is from the company claiming to have sent it. Microsoft's surprise announcement in June that it would begin flagging e-mail in its MSN and Hotmail services that fails a check of the Sender ID protocol sent companies scrambling to initiate compliance. Authentication will help address the problems of e-mail "spoofing" and phishing, and ultimately will lead to a reduction in the percentage of legitimate e-mail that is mistakenly labeled as spam.
  • Consider an E-mail Service Provider. E-mail is a dynamic and complex environment. A good ESP can greatly aid deliverability by providing superior technological capability and know-how, and by continually monitoring, diagnosing and solving deliverability challenges--such as authentication and ISP filtering practices--as they arise. And, because top ESPs oversee deliverability for hundreds of customers, they are able to spot trends much faster than an individual managing e-mail for a single company. Good e-mail vendors don't have to be expensive. For example, one leading web-based provider, Constant Contact, offers e-mail marketing services starting at just $15 a month.

According to eMarketer, this year in the United States, more than 2 trillion e-mails will be sent--more than 228 million e-mails every single hour. And, that number is expected to rise to nearly 2.7 trillion by 2007. Technology is making great strides in separating the good e-mail from the bad. But marketers must be aware of these evolving systems to ensure that their e-mail reaches the recipients who are waiting to get it.