@raiderrobert #nethack very early gained a monster called a "mail daemon". If you had new mail, it would appear in the door to the room you were in, run to you (within your timeslot, so not interference by you) and throw a scroll of mail to you. If you read that scroll, the mail program would be started.
originally, it's symbol was 2 (old people can guess why), but was changed to & like other daemons in a later version.