My issue is this. If you have a system -- any system at all -- which
will "clean" (ie. remove opted out addresses) from a large
spammer's master
list (such as the lists they trade around on CD, you all have
gotten spams
to buy them) then it is inherent that you will be giving them
back a list
of all people on their list not in the opt-out list, and thus
a list of
all people on their list who _are_ on the opt-out list.
What is the risk that you are concerned about here? That the spam
sender might send MORE email to people that don't want it?
If the list has at least as high a percentage of garbage addresses
as the lists do on average it will be useless as a mechanism for
validating addresses. Trying to send mail to the junk addresses will
cause bounces.
In fact ISPs receiving lots of email to closed accounts would have an
incentive to list so the list might well end up having more closed
accounts and other bogus emails than addresses of genuine folk who
want to opt out.
Phill
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