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[Asrg] Re: Asrg digest, Vol 1 #133 - 14 msgs

2003-03-27 12:25:34
From: Markus Stumpf <maex-lists-spam-ietf-asrg(_at_)Space(_dot_)Net>
To: "'asrg(_at_)ietf(_dot_)org'" <asrg(_at_)ietf(_dot_)org>
Subject: Re: [Asrg] My ideas...
Organization: SpaceNet AG, Muenchen, Germany

On Thu, Mar 27, 2003 at 11:04:36AM -0500, Preston, Tony wrote:
The problem has to be solved on the sending end or you do not have
a solution.  The only ideas that seem to make sense are the idea of
validating the sender at each hop (then as more and more MTAs get
updated to do this, the sender is better identified and can be
blocked)
and the idea of estamps.


What exactly do you mean with "validating".
We have some 1000 POP3/IMAP customers that use our mailservers also
for
relaying.
Should we disallow our customers to send emails with a different
envelope sender than the one they have authenticated (SMTP AUTH) with?
How about small companies that host their own mailserver?

What I mean is that if joe(_at_)example(_dot_)com is the FROM user, he should 
exist
on example.com, a query to example.com would check to see if that is
true.

This would at least give you a user on a site that is responsible for
sending.  I realize
that a spammer just sets up the account joe.  What this does do is that
the first hop
from example.com will validate that there is the user joe and add the
validation header
to the email.   Each hop would ask the same question.

This is a lot of overhead in the email, it would happen on every email
on every hop.
The affect would be similar to the tarpit idea since it would hit the
guy doing the
sending with 10000 requests times the hops if he sends out 10000
emails...
Even if the headers are faked, you still know you got the email from the
current
connection, you can record it.  This gives you the ip address of the
spammer
and can be blocked.   If the validation fails, it would have to be
resolved before
the user joe could send email.

Sending email with a different envelope would have to be handled by
having a
validated FROM that will give the "THIS IS OK".   Sending with a fake
email
that will not validate gets the email bounced.

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