hashcash-sendmail and hashcash-request are written by Kyle Hasselbacher.  Both
programs are considered alpha-quality by the author.  Use at your own risk.

hashcash-sendmail is used to add hashcash support for MUAs that do not natively
support hashcash.

hashcash-request is used to pre-request hashcash tokens.

For more information, see http://www.toehold.com/~kyle/hashcash/