I'm really not understanding why you would want to just postpone your emails. Why not just get rid of the widget, and turn off email notifications on your phone, and then just check your email several times a day?
Problem solved.
Other than that, I do not believe there is a way to postpone your emails until the morning, and even then, how would it know if you were sleeping or not, since you fall asleep during a movie etc. Just a hassle.