The postal system was important in the development of modern transportation. Railways carried railway post offices. During the 20th century, air mail became the transport of choice for inter-continental mail. Postmen started to utilize mail trucks. The handling of mail became increasingly automated.
The Internet came to change the conditions for physical mail. Email (and in recent years social networking sites) became a fierce competitor to physical mail systems, but online auctions and Internet shopping opened new business opportunities as people often get items bought online through the mail.