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Re: Massive SPAM Increase

from [gabriel rosenkoetter] Network Security [Permanent Link]
Subject: Re: Massive SPAM Increase
Date: Mon, 16 Oct 2006 11:57:47 -0400 
On Sat, Oct 14, 2006 at 12:17:51PM -0500, Paul Schmehl wrote:

It appears that what you're missing is that this one "flaw" is not enough 
to get mail rejected by policyd-weight.


What you're missing is that the assumption that systems sending
valid mail will always (or even will usually) be listed in DNS is
fundamentally wrong and should never be used even as a weighted
guess to indicate spam.

In fact, what's listed in the MX record in DNS is systems where email
should be sent. For any company larger than 50 employees, that's
probably not the same as from where one could reasonably expect
legitimate email.

DNS provides no assertion about the sending of email, and any system
that operates under the assumption that it does is inherently
broken, because it'll get a false positive on better than half of
the valid emails out there. It's a useless heuristic.

-- 
gabriel rosenkoetter
gr@eclipsed.net

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