>Maybe it is time to see about creating an Internet Standard for ways
>of expressing "postage" or other distinguishing features of non-spam
My main concern with Adam Back's scheme (the only one I've seen mentioned) is that it's purely a cost to the sender, there's no benefit to the recipient. Ideally it should be a transfer of value, but I can't think of too many calculations that the average person would care much about.
But I think the idea of some kind of IETF standard is a good one, as it's a lever for getting such systems incorporated into email software.