Mailbox providers, who derive virtually all their value from the breadth of their customer base, will never purposely degrade the treatment of non-certified messages.

They will if they begin making money not from the people receiving mail, as in the current scenario, but from the e-mailers. The flow of money defines who the customer is => people paying you are your customers. If the customer is the e-mailers then it will be in the ISP's interest to ratchet up the spam filters tighter and tighter and when a company complains tell them to pay to get through.

c) You keep using inflammatory terms: first a “tax”, than “protection racket” and now “kickbacks”. Is “right wing conspiracy” next? Can’t we have a dialog free of that noise?

Goodmail pays ISPs some money it takes in per-email charges. How is this not a kickback? The post office doesn't give any of the extra money it charages for certified delivery to the receivers of certified mail.

This system encourages ISPs to block more mail and force e-mailers to go to Goodmail to get around it, which means more money for the ISP.