ClickZ: Arrival Time and Response Rate Decline

Paul Soltoff argues that marketers should avoid sending email prior to 9 a.m. in order to avoid the "email rush hour." He points out that when people first open their inboxes in the morning, they are generally presented with 8 or more hours of collected emails. He suggest that if you email after 9 or 10 a.m., you will have a better percentage chance of getting your desired response.

While this seems to make sense, it's hard to square with other email experts who maintain that campaigns get the best response rates when they are run between 8 and 9 a.m.