The Complex Science of Mail Sorting: An Overview

The global postal service is an astonishing logistical feat that we often take for granted. From birthday cards and invoices to packages and periodicals, billions of pieces of mail find their way across towns, countries, and continents each year. This immense task is made possible by the intricate science of mail sorting, a system which has seen tremendous advancements over the past few centuries.

The Early Days of Mail Sorting

In its infancy, the mail system was a manual process. Mail sorting clerks sorted incoming and outgoing mail by hand, looking at the address and manually placing each piece into the appropriate bin for its destination. This labor-intensive process required clerks to memorize vast amounts of geographical information, often resulting in errors and misrouted mail.

As populations grew and more people became literate, the volume of mail increased significantly. To handle this surge, postal services worldwide started implementing methods to speed up the sorting process. One such innovation was the introduction of sorting machines, which could categorize mail based on size and weight.

The Postal Code System

A significant breakthrough in mail sorting came with the introduction of postal codes or ZIP codes in the US. The British first established a postal district system in London in 1857. The US implemented the ZIP code system in 1963, allowing mail to be sorted much more efficiently.

The ZIP code is a numerical system that helps designate specific geographic delivery routes within the United States. Each digit in the five-digit code has a specific meaning. The first digit represents a group of U.S. states, the second and third digits together represent a region in that group, and the final two digits represent a specific post office within the region.

The system was later extended to nine digits, allowing for more precise sorting. The additional four digits represent a specific group of addresses within a city or town.

Automation and Mail Sorting

The advent of automation has revolutionized mail sorting. Today, high-speed sorting machines can process thousands of pieces of mail per hour, reading and interpreting addresses, assigning postal codes, and dispatching each item to the appropriate delivery route.

These machines, often using Optical Character Recognition (OCR) technology, can decipher handwritten and typed addresses. If the machine cannot read an address, the image of the address is sent to a human operator for interpretation. Once identified, the address is coded as a barcode, which is then printed on the letter or package. This barcode can be easily read by machines in the later stages of the sorting process.

In addition to OCR technology, mail sorting centers employ sophisticated conveyor and routing systems to physically move mail from one area of the center to another. These systems can automatically route packages and letters based on their size, shape, and destination barcode, dramatically increasing the speed and accuracy of mail sorting.

The Future of Mail Sorting

As we look towards the future, AI and robotics hold great promise for further streamlining the mail sorting process. Artificial Intelligence could enhance OCR capabilities, reducing the need for human intervention even further. Machine learning algorithms could be used to predict and manage mail volumes, optimizing sorting center operations.

Moreover, robotics technology could be utilized to handle packages, reducing the physical strain on workers and increasing efficiency. Some postal services are already experimenting with autonomous sorting robots that can pick up, sort, and place packages in the appropriate bins.

Drones and autonomous vehicles also hold potential for future mail delivery, reducing the need for human delivery drivers and enabling faster, more efficient deliveries, especially in remote or hard-to-reach locations.


The process of mail sorting is a marvel of logistical planning and technological innovation. From humble beginnings to the high-tech operations of today, the mail sorting system continues to evolve, ensuring that our letters and packages reach their intended destinations in a timely manner. As we move further into the 21st century, emerging technologies promise even greater speed and accuracy, ensuring the ongoing relevancy and efficiency of our global postal services.

Leave a Reply

Your email address will not be published. Required fields are marked *