1875, from mail (n.1) + order. Before television and the internet, the bane of retailers and shop-owners.
The origin, foundation and principle of mail order trading is universally recognized as wrong. It was conceived in iniquity and brought forth in despair as the world's greatest destructive medium. Mail Order Trading was born in the brain of knaves and thieves who fired their building for insurance profits, then sold the salvaged and damaged stock to the unsuspecting sons of man in distant territory. [Thomas J. Sullivan, "Merchants and Manufacturers on Trial," Chicago, 1914]