[Having to do crypto for each outgoing spam]
Keep in
mind, they could always simply apply the usual Microsoft solution: throw
more and faster hardware at it. Note also that a lot of spam is already
sent to single recipients per piece. In those cases, the extra costs of
hashing and encryption MIGHT make a SMALL dent, but I doubt it would be
enough to be worth the hassle.
I think the people selling crypto accelerators will be very happy about this...
However, creating new publick/private key pairs is an incredibly expensive operation, and one that a legitimate email wouldn't have to do very often, but a spammer would if we just keep blacklisting their keys.
