Return Path revealed numbers showing a higher proportion of marketer emails were blocked in 2004 by ISPs looking to block out spam than were blocked in 2003. Two of every eleven marketer emails never made it to user in-boxes, up 3.3 percent from the year prior. Road Runner was the most obstinate ISP, blocking more than a third of marketer emails. Earthlink was the most permissive ISP, blocking only 5 percent.