Study: 19% of Opt-In E-Mail is Blocked

The false positive problem is growing, with 18.7 percent of opt-in e-mail now blocked by major ISPs, according to a study by Return Path.

The e-mail deliverability company analyzed 30,000 campaigns sent by more than 100 of its clients in the second half of 2003. The 18.7 percent false positive rate represents a 1.7 percent increase over the first half of 2003, and a 3.7 percent increase over the same period in 2002.

NetZero was the worst offender, Return Path found. That low-cost ISP blocked 37.7 of permission-based e-mail. SBC Global/Yahoo! came in next with 26.7 percent and Mac blocked 26.2 percent. EarthLink had the best record for deliverability, with only 7 percent of opt-in e-mail being blocked.

The problem, of course, is the increasing emphasis ISPs now place on stemming the rising tide of spam. Besides filing lawsuits, ISPs are also hard at work on technological solutions. For now, that largely means filtering — which some believe inevitably results in false positives.

“I think it will not get better over the next year,” said George Bilbrey, general manager of deliverability services for Return Path.

Bilbrey believes e-mail authentication will be a first step toward improving the deliverability problem, but expects the tests going on right now won’t have an impact for at least another year.

“Some better forms of authentication are good first steps,” said Bilbrey. “If they [permission e-mail users] can very firmly establish what their identity is, it’s more likely that their mail would get through.”

Yahoo!’s false positive record was markedly worse than in previous Return Path studies. Yahoo! Mail blocked 16 percent more opt-in e-mail in the period covered by the research, as compared to the previous six months. SBC Global/Yahoo! blocked 14 percent more. Return Path attributed the rise in blocking to the fact that more e-mail is delivered to the bulk e-mail folder, a tactic Yahoo! presumably uses to head off user complaints.’s delivery rates improved most significantly, with a nearly 12 percent gain. CompuServe saw a 10 percent gain.

AOL’s numbers shifted slightly toward improved deliverability. In the first six months of 2003, it blocked around 25 percent of mail, according to Return Path, while the last six months saw it block only around 22 percent. MSN’s delivery figures also changed slightly, but in the opposite direction. The first six months of 2003 saw the ISP block 10 percent of permission e-mail, while the second half of the year saw it block around 13 percent.

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