[Mimedefang] Soliciting opinions on filtering based on bad MX records

[James Ralston]

On 2003-09-11 at 15:25:00-0500 Michael Sims <michaels at crye-leike.com> wrote:
> I've created a new sub called "domainOfSenderHasBorkedDns" (yeah, I
> know how cumbersome that is :) ), which I call in filter_sender.  It
> accepts a sender address and returns true if the domain of the
> address has a "bogus MX record".  I define a bogus MX record as one
> that points to a non-routable address, whether this is 0.0.0.0, or a
> loopback address, or a reserved IP address.

It will probably be a lot simpler just to put this line in your
sendmail.mc file:

    FEATURE(`rhsbl', `dsn.rfc-ignorant.org', `"550 mail from domain " $&{RHS} " is refused because the MX handlers for " $&{RHS} " violate RFC 1123/2505/2821 by not accepting bounce messages - please see http://www.rfc-ignorant.org/policy-dsn.php"')dnl

(Salt the exact message returned to taste.)

You'll need to grab Derek's rhsbl.m4 file in order to use the above
feature; see:

    http://www.rfc-ignorant.org/how_to_domain.php

If you want to be complete, you can use all of rfc-ignorant's
blacklists.  (I only use the DSN blacklist, because that's the one I
submit to.)

-- 
James Ralston, Information Technology
Software Engineering Institute
Carnegie Mellon University, Pittsburgh, PA, USA