snail-mail n.

Paper mail, as opposed to electronic. Sometimes written as the single word `SnailMail'. One's postal address is, correspondingly, a `snail address'. Derives from earlier coinage `USnail' (from `U.S. Mail'), for which there have even been parody posters and stamps made. Also (less commonly) called `P-mail', from `paper mail' or `physical mail'. Oppose email.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.