False-positive filtering remains high among leading email service providers (ESPs) including Hotmail and Gmail, Lyris Research says. Gmail did see a dramatic improvement in Q2 2006, with a false-positive filtering rate of only 2.97% compared to last quarter’s 44%. However, Hotmail’s false-positive filtering, although improving, remains high (18.2% this quarter compared to 23.4% the previous quarter). False-positive spam filtering among European ISPs remains lower, achieving an average rate of only .075% compared to a US average of 3.29%. This is again due to excessive false-positive filtering at two ISPs, cs.com (Compuserve.com), and iwon.com. As well, US ISPs and ESPs are more stringent in their filtering of unsolicited emails which can result in an increase in legitimate emails also being filtered. From a period beginning April 1, 2006 and ending June 30, 2006, the Lyris EmailAdvisor service monitored the full delivery trajectories of 57,836 production-level, permission-based email marketing messages (non-discussion) sent from 57 different businesses and non-profit organizations to multiple accounts at 39 ISP and ESP domains in the United States and Europe.