Yahoo have released CentMail whereby people spend a cent to send an email. By using CentMail, the user's email then includes a signature containing a special key. An example of using CentMail might be to donate $5 to a charity of your choice in exchange for 500 tokens (I presume this allows users to send 500 emails).
The aim is to eradicate spam from in-boxes worldwide. Yahoo do not make money from CentMail as all proceeds go to charity.
In my opinion, this would only work if all users of email the world over used CentMail and all spammers said "no" to CentMail to avoid the cost. If this was the situation, all users could then add 1 filter to their email accounts that said, "if the CentMail signature is not present, then the email is junk". Filtering out spam would become a lot easier.
Unfortunately, I do not see enough people embracing the idea of donating to charity to purchase 'virtual' postage stamps. CentMail may therefore never successfully take off.
If anyone else has any thoughts, your comments are always welcome.
Thanks and take care,
Peter Heylin, BSc (Hons.), H.Dip, MSc