New MH Mail Handling System.
This is the nmh mail user agent (reader/sender), a command-line based mail reader that is powerful and extensible. nmh is an excellent choice for people who receive and process a lot of mail.
Unlike most mail user agents, nmh is not a single program, rather it is a set of programs that are run from the shell. This allows the user to utilize the full power of the Unix shell in coordination with nmh. Various front-ends are available, such as mh-e (an emacs mode), xmh, and exmh (X11 clients).
nmh was originally based on MH version 6.8.3, and is intended to be a (mostly) compatible drop-in replacement for MH.
These tools are mainly useful for writing scripts that manipulating claws-mail's mail folders. Most other mail clients have migrated to maildir.