What Happens to Letters that We Post?

Post office workers collect them to be sent to the people we write to. Much modernization, such as big automated sorting machines for high-speed handling, has affected' the postal service in central cities. And of course big jets now speed air-mail letters to any point on the globe within days. But still most of us think of postal services as just the handy post box or the letter slot, or the faithful postman making his daily rounds. Most countries use numerical codes for addresses to make it easier to sort mail and increase speed of delivery. Large post offices have special machines that can sort letters automatically to speed up delivery.