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Re: [Asrg] Spam detection system proposal

2003-03-05 12:04:29
On Wed, Mar 05, 2003 at 11:47:57AM -0500, David F. Skoll allegedly wrote:

Sorry, wrong.  All bad address removal requires is spamware that
understands SMTP error codes.  No reverse channel of any kind required.

Unless your recipient is running MS Exchange:

http://support.microsoft.com/default.aspx?scid=kb;en-us;304897

or happens to have a Yahoo or AOL account (Yahoo and AOL do not fail
bad addresses at RCPT time.)

Really, did you check?

telnet mailin-01.mx.aol.com smtp
Trying 64.12.136.57...
Connected to mailin-01.mx.aol.com.
Escape character is '^]'.
220-rly-xa03.mx.aol.com ESMTP mail_relay_in-xa3.3; Wed, 05 Mar 2003 12:15:05 
-0500
220-America Online (AOL) and its affiliated companies do not
220-     authorize the use of its proprietary computers and computer
220-     networks to accept, transmit, or distribute unsolicited bulk
220      e-mail sent from the internet.
helo example.com
250 rly-xa03.mx.aol.com OK
mail from: <joe(_at_)example(_dot_)com>
250 OK
rcpt to: <doesnotexist123456(_at_)aol(_dot_)com>
550 MAILBOX NOT FOUND

Not quite at RCPT time, but certainly at SMTP time, which is the same
effect as far as this discussion is concerned:

telnet mx1.mail.yahoo.com smtp
Trying 64.157.4.82...
Connected to mx1.mail.yahoo.com.
Escape character is '^]'.
220 YSmtp mta418.mail.yahoo.com ESMTP service ready
mail from: <joe(_at_)example(_dot_)com>
250 sender <joe(_at_)example(_dot_)com> ok
rcpt to: <Idontexist4567(_at_)yahoo(_dot_)com>
250 recipient <idontexist4567(_at_)yahoo(_dot_)com> ok
data
354 go ahead
subject: reject me
.
554 delivery error: dd This user doesn't have a yahoo.com account 
(idontexist4567(_at_)yahoo(_dot_)com) [0] - mta418.mail.yahoo.com

Besides, low frequency list checking is already routinely done these
days. So low that it can, does, and will keep smart spammers out of
any radar detection you want to set up. It's also so low that they can
deal with bounces. Eg, my vanity domain gets address probes about
twice a day, every day.

It's not enough to say how do we stop spam today, it has to be how do
we stop the evolution of smart, viral, motivated spammers. Your
suggestion makes them evolve to do more list-cleaning. Doesn't sound
like an insurmountable hurdle to me.


Regards.
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