[Dshield] Denying incoming email by reverse lookup of ISP DHCP-ed addresses

David Cary Hart DShield at TQMcube.com
Fri Jun 17 19:49:04 GMT 2005

On Fri, 2005-06-17 at 10:46 -0500, Stef wrote:
> You all know how some of the ISPs started denying email from what are
> home-based accounts, probably by doing a reverse lookup on the
> incoming IP, and looking for strings "hinting" on the dynamic nature
> of that IP assignment (e.g.

> so my question is: does anyone know of a "canned" script, or add-on to
> std email servers (sendmail, postfix, etc.), or a standalone third
> party solution, with all the potential format of name-addresses like
> the above, pre-built - before I start writing my own (perhaps going
> after the email header's IP, and doing a reverse lookup of the
> original IP, and rejecting the ones where the IP x.y.z.w resoved to a
> name containing x-w-z-w ... but I am not sure if this is the rule for
> all ISPs)?!?
A. You can use a DNSBL like SORBS or;
B. Roll your own with RBLDNSD and then rsync our, or someone else's
dnslb file(s).
      * Eliminate Spam:         http://www.TQMcube.com/spam_trap.htm
      * RBLDNSD HowTo:          http://www.TQMcube.com/rbldnsd.htm
      * Multi-RBL Check:        http://www.TQMcube.com/rblcheck.htm

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