One of the distinguishing characteristics of a spammer is the
imbalance between mail sent and mail received. Unfortunately I do not
see a convenient way to penalize people who fall into this category.
One idea about this (although I don't know how scalable it is) would
be, if you could authenticate the sender ie DomainKeys or the like,
then every sender would have a send/receive ratio (somewhere), which
would be entered into the mail header in some way that it could not be
spoofed (more protocol changes though). Then if a mail is received by
the end-user's inbox, it could check the ratio, and decide whether to
accept/reject/quarantine it.
But I sill don't see a way to penalize senders who are rejected too
often. Although perhaps it could be integrated into the 'delay' in
creating the email-stamp/introduction-stamp (the more higher your
send/receive ratio goes, the more it "costs" to send new stuff)
Another possibility is of course law enforecement, but this would seem
to require some centralization of the ratio information, and whose
rejecting what.
The send/receive ratio might also be a problem for mailing lists -
maybe, I'd have to see statistics.
Jim
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