As Internet service providers (ISPs) continue to implement spam-combating systems, more and more permission-based e-mails are being blocked by spam filters, according to a survey by New York-based e-mail services provider Return Path.
More than one-fifth (22%) of permission-based/opt-in e-mail was blocked by the top ISPs during 2004, up from 19% the previous year.
Blocking rates varied widely by ISP, ranging from 5% to 36%. Companies saw the best delivery success at Earthlink, BellSouth, and CompuServe, which blocked only 5%, 6%, and 8% respectively. The most blocking and filtering (36%) occurred at RoadRunner, followed by Mail.com (34%) and Comcast (31%).