I'll re-read your comments, but I think that paying to be able
to send email (again, peanuts for legitimate folks, prohibitively
for spammers) is the easiest and, overall, cheapest solution. Other
solutions have costs as well, of course. In my case, and I don't see
why it isn't typical, paying to send email is a negligible fraction
of my internet-connectivity costs. Note that I don't pay per message
or per byte or whatever, but rather a flat fee. No different, really,
than a flat-rate DSL connection.