Marketers concerned about legitimate e-mail blocked as spam will find confirmation of their fears, a report finds. The costs of such blocking will nearly double, soaring to $419 million in 2008 from $230 million in 2003, according to Jupiter Research (a unit of this site's corporate parent).

Ironically, the percentage of wrongly blocked permission e-mail will drop from 17 percent today to just under 10 percent in 2008, researchers found. However, total spending on retention and sponsored e-mails will increase, accounting for the higher amount of money wasted on messages that are never delivered.

"The report may be just the tip of the iceberg," said Trevor Hughes, executive director of the E-mail Service Provider Coalition (ESPC). "If they're just tracking e-mail marketing, the cost is lost marketing opportunity. But if you count newsletters, paid subscriptions and messages that are a critical component of e-commerce, the cost could be much higher."

The report recommends that marketers use confirmed opt-in practices and says those sending millions of messages should participate in identity-based trusted and bonded sender programs. The latter measure will kick up costs to $0.005 per message from the current $0.002, according to the report.

Companies won't have to look far to find offerings to help them meet the second recommendation. The report mentions IronPort, Habeas and TRUSTe as emerging forces in the nascent trusted- and bonded-sender market.

Worries about permission e-mail ending up in spam filters or simply dumped as spam have mounted for many months, prompting a rash of deliverability services to pop up offering other methods of getting e-mail into mailboxes where it is welcome.

"Because of the deluge of spam and ISPs having to deal with it so aggressively, often well-intentioned marketers or newsletters will have something in their e-mail that makes the ISP think it's a scam," said Jennifer Wilson, VP of marketing for Return Path, another company that helps businesses get their e-mails through.

Many spam filters work by scanning the content of messages, while others block all e-mail from a sender's IP address when complaints reach a certain threshold. E-mail marketers say this leads to a high number of "false positives," when legitimate commercial e-mail is unrightfully blocked.

Some ISPs, including AOL and Yahoo!, allow members to identify spammers with a spam button. However, e-mail marketers have complained that users indiscriminately hit this button, seeing it as a way to unsubscribe from mailings. AOL has said its members use the button 4 million times a day.

Jupiter's report confirms these charges, citing another study by e-mail marketing firm Bigfoot Interactive in which 67 percent of consumers surveyed said they believed clicking the "this is spam" button or "report spam" link would unsubscribe them from e-mail lists.

In addition to using third-party trusted sender programs, marketers should make the permission and opt-out process easier by following four steps, according to the report. Companies should clearly state the date and time when customers opted in; they should send e-mails only for a limited period of time or make customers opt back in after a specified period of time; they should make opting out easy and make relevancy the ultimate determinant of e-marketing frequency.

"What they're getting at [in the report] is that when you are sending e-mail to someone you have to make sure you're sending something they're expecting and they want. If they're not engaged in that e-mail it doesn't matter if they opted in, they are not going to read it and it's going to be spam to them," said Wilson.

"Companies are going to have to put some resources behind managing their e-mail and making it as relevant as they can," Wilson noted. "If they can, their response rates will go up and deliverability will rise because they won't have as many complaints about their mail."