We all have keys to lock and unlock our homes, offices, vehicles and other critical items in our lives. What then, you may ask, do keys have to do with mailing? To aid in the proper identification of postal facilities, particularly in eDoc, the USPS has assigned unique identification codes, called Locale Keys, to each postal processing and delivery facility. This allows for very precise identification of the postal facilities that mailers are using for their origin entry and for any additional entry points at which mail is entered.
Read more: https://www.windowbook.com/Learning/Postal-Concierge-E-tips