Other processing machines read the bar codes and direct the letters into bins based on ZIP codes - this indicates the next processing plant, in the region where the letter will ultimately be delivered. If the scanner can't read the address, the letter is manually sorted. An optical scanner scans the address, and then a bar code representing the specific address is sprayed on the front of the envelope. Your letter gets its postmark, and machines print cancellation lines across postage stamps to prevent them from being reused.Ī unique bar code is imprinted on the back of each piece of mail.

They also orient the packages so their addresses are right-side up and facing the same direction. There, all of the mail is placed on a truck and taken to a mail processing plant.Īt the mail processing plant, machines separate mail by shape and size. The 5 digit zip code most commonly indicates a destination post office.Ī postal carrier collects your letter from the box along with the rest of the mail and takes it to the post office. USPS five-digit zip codes are the zip codes you are familiar with.

4 digit zip code lookup