In today's lecture, we'll discuss the history of the postal service. Initially, letters were carried by messengers on foot or horseback. In the 19th century, the introduction of the railway dramatically sped up mail delivery. However, it was the invention of the postage stamp in 1840 that revolutionized the system, as it shifted the cost from the receiver to the sender. Later, airmail began in 1911, but it wasn't until the 1930s that regular transatlantic flights carried mail. Today, email has largely replaced traditional letters, yet postal services still handle parcels and official documents.