jwol3 - 12:53 pm on Mar 28, 2007 (gmt 0)

eROI publishes quarterly stats for free. Mondays have been hot recently. My gut is that aggregate data like that is a good guide, but not a replacement for testing. I've found Fridays to work well for messages with a single call to action, but items with lots of links, like newsletters to work better mid-week.

I was reading something a couple months ago about mailers who got a huge boost from separating home from work emails - hit the work ones Tue-Thur, but hit the home ones on Sunday and that created a huge lift.