The program counts your mail and tells you about it rather obnoxiously.
The program first appeared in Nx 1.3 . was first written by An Noah Friedman Aq firstname.lastname@example.org in 1993. This version was written by Charles M. Hannum Aq mycroft@NetBSD.org .
The read loop is horrendously slow on every shell implementation tried. uses from(1) and wc(1) instead, though these are not shell builtins.