I totally agree. No kind of filtering (and I have significant experience
in this) works to stop spam.
I already said this on nanog, in my opinion we need to develop system
that allows ISP mail servers to identify and certify each other (most
likely though chained certificates,
I don't think that will work either. It fails the robustness test --
it is too easy for a system like that to fail.
I think among other things it is time that we started treating
stealing other people's open relays for purposes of forwarding
commercial email as what it probably is -- a felony. That won't help,
though, so long as no one attempts to prosecute it.