I can think of one possible solution to the spam mess... at least, a general concept, but not the "nuts and bolts" of how it would be implemented.

What if sending emails were no longer free? A monthly reverse sliding scale could be assessed, something like:

1-1000 monthly emails: free
1001-10,000 monthly emails: 1 cent apiece
10,001-100,000 monthly emails: 10 cents apiece
100,001+ monthly emails: $1 apiece.

Who would assess these fees, who would regulate them, collect them, etc. I leave as an excercise for the reader.

tanstaafl.
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"There Ain't No Such Thing As A Free Lunch"