Fridrik Skulason wrote:
This is, quite frankly, nonsense.
You are forgetting the fact that in the case of compromised (zombie)
machines, the extra cost would fall on the owners of those machines, not
the spammer - the extra cost would not make one bit of difference to
those spammers. True, it would be a problem for spammers using
throwaway domains or dedicated spam sites, but they can be blocked
today with other means.
Today there's no real reason to use throwaway domains, though. It's not
until SPF becomes common that spammers will be forced to resort to
them. Why bother when they can just forge a bunch of spam from
foobar(_at_)aol(_dot_)com or support(_at_)microsoft(_dot_)com?