In <20031014224831(_dot_)GA15773(_at_)thyrsus(_dot_)com> "Eric S. Raymond"
<esr(_at_)thyrsus(_dot_)com> writes:
[...] The bind we can set up, given widely
deployed SPF, is that
(a) If a spammer spews with an IP/domain combination that doesn't match,
he loses -- the BL's spam traps ignore him, but all SPF-aware MTAs send
the mail to /dev/null.
(b) If a spammer spews with an IP/domain combination that *does* match,
SPF-aware mailers won't bin his stuff, but spam traps catch it and
the BL eats his his domain.
So a two-layer check should work pretty well.
Exactly.
The SpamCop DNSBL is able to catch new spammer activity from an IP
address very quickly, often in a matter of only a few hours. While
domain names may not be that expensive (and their price will continue
to fall), that still is going to be a chunk of change that a spammer
will have to spend. More over, this knocks out the casual spammer, or
the spammer who thinks they are legitimate.
-wayne
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