Oh goody. I've been wanting to use this since my slashdot days... today is my first chance!

Your post advocates a

[x] technical
[ ] legislative
[ ] market-based
[ ] vigilante

approach to fighting (ML-generated) spam. Your idea will not work. Here is why
it won't work. [One or more of the following may apply to your particular idea,
and it may have other flaws which used to vary from state to state before a bad
federal law was passed.]

[ ] Spammers can easily use it to harvest email addresses
[ ] Mailing lists and other legitimate email uses would be affected
[ ] No one will be able to find the guy or collect the money
[ ] It is defenseless against brute force attacks
[ ] It will stop spam for two weeks and then we'll be stuck with it
[ ] Users of email will not put up with it
[x] Microsoft will not put up with it
[ ] The police will not put up with it
[x] Requires too much cooperation from spammers
[x] Requires immediate total cooperation from everybody at once
[ ] Many email users cannot afford to lose business or alienate potential employers
[ ] Spammers don't care about invalid addresses in their lists
[ ] Anyone could anonymously destroy anyone else's career or business

Specifically, your plan fails to account for

[ ] Laws expressly prohibiting it
[x] Lack of centrally controlling authority for email^W ML algorithms
[ ] Open relays in foreign countries
[ ] Ease of searching tiny alphanumeric address space of all email addresses
[x] Asshats
[ ] Jurisdictional problems
[ ] Unpopularity of weird new taxes
[ ] Public reluctance to accept weird new forms of money
[ ] Huge existing software investment in SMTP
[ ] Susceptibility of protocols other than SMTP to attack
[ ] Willingness of users to install OS patches received by email
[ ] Armies of worm riddled broadband-connected Windows boxes
[x] Eternal arms race involved in all filtering approaches
[x] Extreme profitability of spam
[ ] Joe jobs and/or identity theft
[ ] Technically illiterate politicians
[ ] Extreme stupidity on the part of people who do business with spammers
[x] Dishonesty on the part of spammers themselves
[ ] Bandwidth costs that are unaffected by client filtering
[x] Outlook

and the following philosophical objections may also apply:

[x] Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
[ ] Any scheme based on opt-out is unacceptable
[ ] SMTP headers should not be the subject of legislation
[ ] Blacklists suck
[ ] Whitelists suck
[ ] We should be able to talk about Viagra without being censored
[ ] Countermeasures should not involve wire fraud or credit card fraud
[ ] Countermeasures should not involve sabotage of public networks
[ ] Countermeasures must work if phased in gradually
[ ] Sending email should be free
[x] Why should we have to trust you and your servers?
[ ] Incompatiblity with open source or open source licenses
[x] Feel-good measures do nothing to solve the problem
[ ] Temporary/one-time email addresses are cumbersome
[ ] I don't want the government reading my email
[ ] Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

[x] Sorry dude, but I don't think it would work.
[ ] This is a stupid idea, and you're a stupid person for suggesting it.
[ ] Nice try, assh0le! I'm going to find out where you live and burn your
house down!