Mail art

Mail art is art which uses the postal system as a medium.
Mail art is also, simultaneously, a message that is sent, the medium through which it is sent as well as one of the longest-lasting art movements in history. To be precise, an amorphous international mail art network evolved of thousands of participants in over fifty countries between the 1950s and the 1990s from the work of Ray Johnson and influenced by earlier groups, including Dada, the Surrealists and Johnson's contemporaries in the Fluxus group. Mail artists characteristically exchange ephemera in the form of illustrated letters, zines, rubberstamped, decorated or illustrated envelopes, artist trading cards, postcards, 'artistamps', mail-interviews and three-dimensional objects.
Whether or not one is a formal mail artist, there exists a rich history of creative products sent through the post to draw upon. The most familiar example is the illustrations on envelopes carrying first day issue postage stamps, which philatelists refer to as first day covers, but mail art encompasses other "decorated envelopes" as well as a wide range of other procedures and media such as rubberstamping and the creation of artistamps. Mail art is traditionally, though not always, distinguished from simply "mailed art," which is art that does not truly use the postal service but is simply regular art when sent through the mail.
Mail artists like to claim that mail art began when Cleopatra had herself delivered to Julius Caesar in a rolled-up carpet (though this was arguably neither mail nor art). However, perhaps the initial genesis of mail art was in postal stationery, from which mail art is now typically distinguished (if not defined in its broadest sense). The first example of postal stationery was the pictorial design created by the English artist William Mulready (1786-1863) for mass printing-press reproduction on the first stock of prepaid postage wrappers or envelopes produced for the launch of the Penny Post in Britain in 1840. Mulready's design was not well-received by the public and various cartoonists and artists produced lampoon versions. However it was recognized that an innovative and powerful communication adjunct piggybacking on the basic letterpost service had become available, and over the next 50 years or so millions of pictorial envelopes with a wide variety of motifs and designs were processed by postal services worldwide.