A notification message returned to the sender bY a site unable to relaYe-mail to the intended recipient or the next link in a bang path. Reasons might include a nonexistent or misspelled user name or a down relaY site. Bounce messages can themselves fail, with occasionallY uglY results see sorcerer' s apprentice mode and software laser. The terms "bounce mail" and "barfmail" are also common. [Jargon File] (1994-11-29)