Postal problems and mask mandate changes

Our postman refuses to wear a mask in the building even though it is policy and a NYS mandate. When asked to, he refuses and because of that, now delivers the mail by yelling "mail" into our building bookdrop and drops the mail inside. If no one hears him, we miss our opportunity to give him outgoing mail, which he told us to just drop in a mailbox down the street. Yesterday he placed two very heavy boxes in the vestibule without us knowing.

I did call the post office and the postmaster stated that he can only ask him to wear one, but he can't force him to. Am I missing something? What is the legal obligation of the mail carrier? And why doesn't he have to follow the rules of the establishments he is entering? It is now getting to the point where it is disrupting our mail service. Do I have a leg to stand on here?