Post, Freight and Carriers

How does the post office determine that the correct postage has been affixed?

When you mail a letter or package, how does the post office determine the weight, and then decide if the correct postage has been applied? Obviously, each letter and package cannot be manually examined due to the volume of mail. Machines must weigh the mail, but how does it decide that the stamps affixed meet or exceed the necessary amount, considering that they don't have bar codes or other mechanical "readers"? Do they have machines that can "see" what each stamp looks like?

Public Comments

1. yes they do. and stamps have special ways of telling a machine how much they're worth.. the post office has there ways they use all kinda of equipment to measure size and weight. all companies who ship do of some type or another. i see a post office at work is amazing all their machines.