A mail user agent written in Tcl. The description below is a bit old. As of 2003, the current version is 2.6.*. There is a Wiki just for exmh at [L1 ]

 What: exmh
 Where: http://www.beedub.com/exmh/ 
 Description: A Tk based UI to MH.  Supports nested folders, MIME/metamail,
        pre-sorting mail into different folders before you read it,
        searching for URI/URL/URN references, etc.  Requires MH
        mail-handler, metamail, the faces library, and expect.
        The wizzy tar file is a package that allows exmh users to
        click on mailto links within Netscape and launch an exmh compose
        window.  Tom Phelp's web page points to code to add Glimpse support
        to exmh for full text searching of your mail files.
 Updated: 10/2001
 Contact: mailto:[email protected]  (Brent Welch)
 What: folderbiff
 Where: From the contact
 Description: Tk program to watch MH/slocal folders and, when button clicked,
        start up an exmh session on a folder that gets new mail
 Contact: mailto:[email protected]  (Bill Burdick)
 What: nn-tk
 Where: http://www.general.uwa.edu.au/u/toivo/nn-tk 
 Description: A Tk interface to nn (net newsreader).  It allows
        the use of exmh to post news, as well as to
        send and read MIME and PGP email messages as well as to turn URLs into
        buttons for passing to Netscape or other browsers.  Supports Tk 4.x
        You may need to update to the latest version of exmh to get the
        support for all of nn-tk's features.  Be sure to keep checking
        back at the ftp site for new releases.
 Updated: 08/1998
 Contact: mailto:[email protected]  (Toivo Pedaste)
 What: tkNewMail
 Where: http://www.schooner.com/~loverso/tcl-tk/ 
 Description: Tk 4.1 replacement for xbiff.  Can report on new mail in
        several ways, including using POP directly, or using MH folders,
        can work with exmh, and includes a clock.
 Updated: 12/1998
 Contact: mailto:[email protected]  (John Robert LoVerso)