How Do Post Offices Sort Mail?

Large central mail processing facilities are located between the various post offices they serve to distribute mail efficiently. These processing facilities have mail-sorting equipment that can handle standard letter-size mail. Individual post offices report the order of their mail delivery routes to these central processing facilities. The individual addresses are keyed into the sorting equipment computer in the order in which they are delivered. Then each day, letter-size mail is sent through the sorting equipment to place it into delivery order for individual mail carriers. The presorted mail (DPS) is placed in mail trays and delivered every morning along with parcels and unsorted mail pieces to every post office. This presorted mail can be taken by mail carriers directly to the street to be delivered. Individual carriers may place this mail into their sorting case along with larger pieces to avoid working from several trays while driving.

Each individual mail route has a case set up where a carrier sorts mail pieces into the order in which they will be delivered. The mail case is similar to bookshelves placed in a U pattern surrounding the mail carrier. The shelves are divided into small slots 1 to 2 inches wide. Each slot has an address for each customer address that mail route serves, usually between 250 and 700 mailboxes. The carrier memorizes the order of the route and the location of each mini mailbox on the case. The carrier places mail pieces into this case each morning in delivery order. When all the mail for the day is in the case, the carrier pulls the mail back down and places into trays for transport and delivery that day. About half of the established route time is spent casing mail, and the other half is spent delivering mail. For example, a carrier with an 8-hour mail route with 550 individual mailboxes to deliver would spend 3 to 4 hours casing the mail and the remaining 4 to 5 hours delivering the mail.

Mail arrives early at the post office, usually before the postmaster and mail carriers arrive for the day. The postmaster or postal clerk pulls the large metal cages of mixed mail into the post office and opens them. Then, the postmaster divides the parcels, magazines, large envelopes and other flats for the mail carriers and postal boxes. The postmaster has a sorting system that may involve tubs or shelves for dividing the mail by route. An assigned number identifies routes, for example, route one and route two. The postmaster does not put the mail pieces into delivery order, just places them in the correct area for the route number. After dividing mail pieces for delivery routes, the postmaster or clerk will sort individual mail pieces into the post office (PO) box section, placing each mail piece manually into the correct post office box.