Mutt is small but very powerful MIME mail client for unix operating systems,
similar to PINE, ELM and MUSH.  It is highly configurable (including key
bindings), allows sorting by threads, and has support for color terms (using
ncurses or S-Lang).

Mutt's home page is http://www.cs.hmc.edu/~me/mutt/
The ftp site is ftp://ftp.cs.hmc.edu/pub/me/mutt/