On Wed, Mar 19, 2003 at 10:21:41AM -0800, Justin Mason wrote:
Also, requiring rDNS is not even that effective a test; our rule for this
condition in SpamAssassin gets this rate:
35.5901 3.0576 0.921 0.78 1.33 NO_DNS_FOR_FROM
in other words 35.59% of spam has no rDNS, but 3.05% of ALL nonspam mail
does too. The latter is bad news, it's a *very* high false positive rate.
I should note that our rDNS is based on the calling MTA, NOT the envelope
FROM domain.
Again, if you have a means for users to "poke a hole through the block" in
a fashion that requires no intervention on the part of the mail admin (which
is the case with us) it allows the site to be more aggressive with rules
such as this.
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