Fighting Spam with <User Unknown> messages.

Ian Andrew Bell (
Mon, 01 Mar 1999 11:35:23 -0800

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Typically, those guys who sell SPAM lists are now promising to
"guarantee" that all email addresses that they have harvested are real,
operational email addresses. To me, this implies that they are sending
out test SPAMs and waiting either for you to try to unsubscribe yourself
(which oddly never seems to work) or for no reply at all -- indicating
that it's reached an active recipient.

BUT, if they do receive a reply from SMTP that claims a "User Unknown"
error I'll bet they delete that address from their data set

SO, what's needed is a convenient way for our hero, the End User, to
generate fake "User Unknown" messages to bounce back to SPAMmers

Unfortunately, to make it look legit you'd have to change your name &
email in your preferred client which is way too inconvenient. And you
wanna do it fast before the SPAMmer's email address gets invalidated by
their ISP.

One way to do this could be a web page. Specify a mailhost and your
email address on a form, along with the spammer's address. Have the CGI
open an SMTP connection directly to the spammer's mail server and spoof
a reply from the mailhost you specified. Insert a generic User Unknown
message quoting your email address and Bob's your uncle!

I'd do this, but it requires some creative SMTP/TCP spoofery that I
don't fully understand. Also I haven't written actual code in years,
and HTML bores me.

Anyone wanna discuss this? Let's get some VC and build a startup around
this! Maybe @Home will buy us out! (joke)

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tel;pager:(800) 365-4578
tel;cell:(408) 921-4873
tel;fax:(408) 526-4287
tel;home:(408) 564-2523
tel;work:(408) 525-8630
org:Cisco Systems - Service Provider LOB;Telephony Internet Services Unit
title:Product Manager
adr;quoted-printable:version:2.1;;Building SJ-E2=0D=0A170 West Tasman Drive ;San Jose;CA;95134;USA
fn:Ian Andrew Bell