I had a similar thought a few months ago. Actually with DigiCash there is a specially nice feature from the point of view of the remailer. Suppose the cash is embedded in the message headers itself. The remailer receives the message with the cash in it, turns it in at the bank to make sure it is good, and withdraws a new blinded coin which it sticks in the headers of the outgoing message. The eventual recipient of that message can then have his software turn in that coin and if it is good that raises the priority of the message for him to read. The nice thing is that if the recipient doesn't have the DigiCash software, he will never cash the coin. That means that the remailer can, after a delay, reclaim uncashed coins for its own use. It doesn't have to charge postage explicitly, but it benefits as a middleman from unclaimed postage. This would also of course encourage people to learn to use digital cash so they could take advantage of these pennies from heaven in their mailboxes. Hal