"Mail art is art which uses the postal system as a medium... Mail artists typically exchange ephemera in the form of illustrated letters, zines, rubberstamped, decorated or illustrated envelopes, artist trading cards,postcards, artistamps, faux postage, mail-interviews, naked mail, friendship books, decos, and three-dimensional objects."
"Naked Mail is a form of Mail art wherein the sender will send an item in the postal system without any sort of wrapping or protection that one might normally use, such as envelopes or Kraft paper. Due to its tendency to aggravate postal employees, Naked Mail is sometimes referred to as TTPO which stands for "Torture The Post Office"... The purpose of sending naked mail is varied - some ask for participation from the postal workers themselves (such as cameramail) and incorporate that into the art. Others simply just want to see if their item will make it at all to its destination (such as those sent in the P22 mail art project)."