Contrary to conventional wisdom, Fridays had the highest open rates for email messages in 2005, according to a new report from ExactTarget, writes Internet Retailer. The average open rate for Fridays was 39.6 percent, with Thursday right behind at 39.0 percent. Sundays, however, had the highest click-through rate: 6.9 percent. Open rates by day of week were as follows: Friday, 39.6 percent; Thursday, 39 percent; Wednesday, 38.4 percent; Tuesday, 38.4 percent; Monday, 37.9 percent; Sunday, 33.5 percent; Saturday, 31.5 percent.

Click-through rates by day of week were as follows: Sunday, 6.9 percent; Friday, 6.5 percent; Thursday, 6.4 percent; Monday, 6.4 percent; Tuesday, 6.3 percent; Wednesday, 6.1 percent; Saturday, 6.1 percent.

Morgan Stewart, director of strategic services at ExactTarget and author of the study, confirmed, however, that "there is no such thing as a universal best day to send email," adding, "organizations must conduct their own tests to determine which day of the week works best for them."