The trouble with modern technology is that anyone can try to reach you, at any time. Your boss can leave a passive aggressive email at the top of your inbox overnight, so you see it when you want to check personal mail. Anyone can send you an SMS or iMessage. And anyone with your phone number can spam you, any time.
Currently in iOS, you can block iMessage senders. But in iOS 13, you gain two new ways to keep stalkers, weird friends and over-sharing co-workers out of your digital life. Now you can block unknown phone callers and email senders.