Top Internet service providers blocked 17 percent of legitimate permission-based e-mail in the first half of the year, according to a report issued by Return Path.
The company, which helps e-mail marketers make sure their mail gets through, said the so-called false-positive rate at the top dozen ISPs in the first two quarters of the year dropped 2 percent from the fourth quarter of 2002 and 5 percent from the third quarter.
While improving, the Superior, Colo., firm said e-mail improperly blocked by stringent filters at ISPs represented a major challenge for the e-mail marketing industry, as the consumer backlash against spam leads ISPs to aggressive action against bulk e-mail. Many e-mail marketers have complained that the filters swoop up their legitimate e-mail messages along with spam.
Return Path based its findings on nearly 10,000 e-mail campaigns it monitored for clients using its Mailbox Monitor service. Return Path acquired Mailbox Monitor when it bought Assurance Systems in June.
Return Path found that the false-positive rate varied wildly at ISPs, from as low as 1 percent to as high as 46 percent. Among major ISPs, AOL gave e-mail marketers the most fits, with a 25 percent rate. AOL, struggling to hold onto its 28 million subscribers, has made its robust spam-fighting capabilities a key part of its marketing. AOL has said that spam is its top consumer complaint by far.
Interestingly, Earthlink, which has vied with AOL for top anti-spam credentials, had one of the lowest rates at 7 percent. Yahoo! took top honors with a mere 4 percent false-positive rate. MSN's rate was just under 10 percent.
Return Path found catalogers most vulnerable, suffering a non-deliverability rate of more than 40 percent. Software also suffers a high number of undelivered e-mail, with nearly a third not getting through. In contrast, Return Path found clients in retail, software and non-profit industries had non-deliverability rates under 10 percent.