I've been heavily involved with direct marketing and email marketing for years, I can tell you this is not a rule that is set in stone. Yes, generally spoken, t

I've been heavily involved with direct marketing and email marketing for years, I can tell you this is not a rule that is set in stone. Yes, generally spoken, the opening rate is lower on Fridays. But that doesn't mean conversion is lower, too. I've sent mass emails on Saturday evenings that converted like crazy, only to fail miserably the next week at the exact same time. Plus, if nobody sends emails on Friday because they 'don't open well', you're the only one sending them. Keep your content quality, relevance and value to the subscriber as high as possible, and the time won't matter.