It depends on your audience, and it depends on their connection to you. A few of our clients find the best results in reaching their busy, C-level contacts at 4am on weekdays or 6am on Sundays. Many like to release their emails on Tuesday or Thursday during traditional business hours (e.g., 9am or 3pm). We schedule a lot of Campaign Resends (a resend to the people who didn’t open the first release) on Friday mornings and Monday afternoons. Why such a mix? Because studies show that we open emails based on who they are from. If we know, like, and trust the sender, we’ll then consider if the content — revealed in the subject line – is of interest.