Twenty-two percent of permission-based e-mail overall was blocked by the top ISPs in 2004, according to Return Path. E-mail mistaken for spam continues to be a growing problem, with an increase of 3.3 percentage points.
Return Path said blocking for each campaign measured varied from a low of 1% to a high of 57%.
Companies saw the best delivery success at Earthlink (5% blocked), BellSouth (6% blocked) and CompuServe (8% blocked). The most blocking and filtering occurred at RoadRunner (36%), followed by Mail.com (34%) and Comcast (31%).
Meanwhile, e-mail marketing company DoubleClick on Tuesday released its Q4 2004 E-mail Trend Report. According to the report, the average delivery rate grew to a high of 90.6% in the fourth quarter of 2004, a year-over-year increase of 3.8% from fourth-quarter 2003, when it was 87.3%.