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 items are either left as-is or artistically altered. A postage stamp and the address of the person who is to receive the item is then placed clearly marked on the item and sent.
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).
Compact discs are often used as vehicles for mail art as they are small and lightweight, requiring usually only the regular letter mail rate. Often they are decorated, such as being painted or decoupaged, and sent.