According to a study by Lyris, false-positive filtering (emails that are incorrectly identified as unsolicited or "spam" emails) remains high among leading email service providers (ESPs) including Hotmail and Gmail. Gmail did see a dramatic improvement in Q2 '06, with a false-positive filtering rate of only 2.97 percent compared to last quarter's 44 percent. However, Hotmail's false-positive filtering, although improving, remains high (18.2 percent this quarter compared to 23.4 percent the previous quarter).
"While false positives are increasing among some ESPs, the industry as a whole is winning the fight to reduce the amount of spam," says Dave Dabbah, Director of Sales and Marketing, Lyris Technologies. "As ESPs become better and more discerning in identifying spam, the result will be a decrease in filtering of legitimate email as well. However, marketers can do their part too by becoming more aware of what is likely to get their emails incorrectly filtered."
False-positive spam filtering among European ISPs remains lower, achieving an average rate of only .075 percent compared to a U.S. average of 3.29 percent. This is again due to excessive false-positive filtering at two ISPs, cs.com (Compuserve.com), and iwon.com. As well, U.S. ISPs and ESPs are more stringent in their filtering of unsolicited emails which can result in an increase in legitimate emails also being filtered.
Download a complete (pdf) copy of the study here.