21% of permission-based e-mail was not delivered in the first half of 2005

Top ISPs and web-based email providers did not deliver 21% of permission-based emails to consumers’ inboxes during the first half of 2005, according to Return Path. In 2004, 22% of permission-based email was not delivered. Blocking rates varied widely by ISP, ranging from a low of 8% to a high of 39%. Companies saw the best delivery success at Mac.com, which only blocked or filtered 8%, and Earthlink and USA.net, which each blocked 10%. Excite and Gmail blocked or filtered the most permission-based email (39%), followed by MSN (33%) and Hotmail (32%).