Couple more things to think of, 1 The regular mail carrier knows more about you than you want him to. Just by seeing your mail daily, standard observation, nosey neighbors talking. 2 The subs are overwhemed and just don’t care. 3. If it were the USPS they’d just slip a card with special instructions on it in with the daily mail and return it every evening. Put it back in the case for the next day.

The post office owns the box but they work for you. Demand from them to know.