If you mail a letter, and mail it before the cut-off time that day, it can't possibly get there before the next day's mail delivery. It will probably take 2 or 3 days. Mail always gets picked up, goes to a central processing place to get sorted, and then gets sent to where it's going. Given that, you could obviously get something there sooner if you drive it there yourself and the destination is only an hour away. But then you spend two hours or more of your time, and the gas, to do that. If you drop something in a mailbox, you spend maybe 15 minutes of your time and a dollar or so on postage..