Hashcash Filter for Mutt


This is a small filter program written in Perl that reads a mail message from STDIN, adds Hashcash headers, and then forks sendmail and writes the result for delivery.

It handles Bcc recipients by sending a separate message for each recipient and appending a single X-Hashcash header to each. The program runs in the foreground, so you, the sender, must wait the time necessary for the hashcash tool to mint all the necessary tokens. This is a minor annoyance. Still, it works for me, and I prefer the simplicity over the infrastructure needed to support a server to handle background minting. If you'd prefer that, take a look at Kyle Hasselbacher's far superior hashcash-sendmail, which is also probably more reliable than this script.

It is quite likely that this script will work with other mail sending programs besides mutt. No guarantees, though.