cl-sendmail is a hack of Christophe Rhodes' sendmail.lisp file found
It depends on the software found at
which are all available through recent quicklisp versions,
together with the other dependencies:
babel-streams external-program trivial-gray-streams
While originally written for SBCL, it now should work with CMUCL
(thanks to Tim Howe) and Allegro CL (patches by Utz-Uwe Haus).