Wikipedia
A Mailgram is a type of telegraphic message which is transmitted electronically from the sender to a post office and then printed and delivered to the recipient via postal means.
Western Union invented the Mailgram in 1970. Service via Westar, Western Union's own communications satellite, was introduced in 1974.
The advantage of Mailgrams over postal mail was speed and verifiability of transmission; they were widely used in official notifications and legal transactions. Their advantage over full-rate telegrams was lower cost while still maintaining the look and feel of an important Western Union Telegram. The Mailgram quickly became a widely used medium for business-to-consumer communications.
Although iTelegram still provides a mailgram service in the United States, Western Union discontinued all telegram messaging, including Mailgram, in 2006.