Rules and exceptions to the best day
I too have heard and experienced that Tuesdays are best followed by Thursdays. But I was sent an email at 4AM on New Years Day by none other than Dan Kennedy, the guru's guru of marketing.
I have to assume that he does very little of his marketing by chance. Things are well thought out. But as I look back over recent emails I've received from him, I received an email on Christmas day (by the way, entitled, "The Secret to direct mail success") and Thanksgiving (is this a pattern?). His emails come regularly on Mondays, Thursdays and Saturdays. And these are B to B emails.
So go figure!