I’m not too familiar with the stealth addresses so I can’t comment on this. I didn’t quite understand the analogy. This is exactly how cash works today and with the digital version of cash (e.g. Grin) having the benefit that you don’t need to synchronize in time nor do you need to meet at the physical location which makes the distance between you and the person you want to exchange with irrelevant (postman in your example). You only need to exchange 2 messages at any time from any location. Why interactivity is so bad in the minds of many people is still a mistery to me to be honest. It’s magnitudes more practical compared to the cash we have today.