The United States Post Office has operated for the duration of the COVID crisis, and has been hugely instrumental in the vast increase in online sales - fuelled by the compulsory closing of retail establishments. Here is a private mailbox in rural Connecticut. Generally speaking, you don’t find letterboxes outside towns or cities by virtue of wide population disbursement and the impracticality and cost of servicing them. So, a raised flag on the side of your mailbox alerts a passing postman who collects the mail.
