Description:

Nmh is an email system based on the MH email system and is intended
to be a (mostly) compatible drop-in replacement for MH. Nmh isn't
a single comprehensive program. Instead, it consists of a number
of fairly simple single-purpose programs for sending, receiving,
saving, retrieving and otherwise manipulating email messages. You
can freely intersperse nmh commands with other shell commands or
write custom scripts which utilize nmh commands. If you want to use
nmh as a true email user agent, you'll want to also install exmh to
provide a user interface for it--nmh only has a command line interface.

If you'd like to use nmh commands in shell scripts, or if you'd like to
use nmh and exmh together as your email user agent, you should install
nmh.