(FAQ) What is Hashcash

What is Hashcash?

MDaemon is now able to generate hashcash stamps. Hashcash is a form of electronic postage designed to help verify that the sender of an email message invested sufficient effort in order to do so. Effort is measured in terms of CPU use. Now that hashcash verification is support system and inserted into outgoing messages will have a real impact on lowering the false positive rates when your users send mail. A new screen was added to the Spam Filter properties to configure hashcash settings.

In order to stamps to be generated and inserted into messages the message must have arrived to MDaemon over an authenticated SMTP session. Stamps are never generated for list messages. Finally, only messages either FROM or TO an address listed in HCMint.dat will be stamped. You can configure all this from within the Hashcash properties in the GUI.

In order to honor hashcash stamps for incoming messages your domains must be listed in the \SpamAssassin\Rules\80_MDaemon_Hashcash.cf file. The installer has already enabled all users of your primary domain for this. To see how it is done for other domains just open the file with notepad and read the instructions there.

For more information on HashCash and to support the HashCash concept visit http://www.hashcash.org/. 

Additional Comments

This feature requires MDaemon Pro.