Extra precautions should be taken with the copper or brass mailbox doors, and the brass and copper flag (if applicable) because they are handled more frequently. Waxing brass or copper mailboxes with car wax every time you wax your car should prevent any problems. Wax powder-coated mailboxes several times per year for long-lasting good looks. Oil or grease applied to the door hinges and where the flag hinges is also a very good idea.