[Asrg] Reverse DNS requirement

On Tue, Jun 17, 2003 at 01:09:37PM +0200, Markus Stumpf wrote:
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> And I surely don't stop aguing that a TXT record with the contents
> "MAILSERVER" in reverse DNS would be much faster and easier deployed
> and effective than RMX or companions. And it would save us from
> accepting email from all the broken workstations, homecomputers, open
> proxies and virus infected hosts that never had been intended to be a
> mailserver.

Amen!  This is similar to what we'd like to see.  We are presently
requiring reverse DNS for IP addresses of MTA's which connect to our MX
(with exceptions, which are dwindling).  This has nothing to do with the
MAIL FROM domain, it simply means that if you connect to us, your IP address
must have a name, and that name must map back to your IP address.  What you
suggest above is exactly the sort of next step we're looking for; namely,
a DNS RR which tells the world that a particular host name has been designated
as an MTA (outgoing at least).  I would suggest something like:

myhost.mydomain.com.	MTA	"abuse@mydomain.com"

This also requires you to specify an abuse address for that MTA.
Since this does introduce another RR, a TXT record could be recognized as well:

myhost.mydomain.com.	TXT	"MTA:abuse@mydomain.com"

Unlike other proposals, this one does not relate the MAIL FROM domain with
the connecting IP or the HELO line.  It simply states that the host name in
question is in fact intended to be an MTA.

Reverse DNS, when applied to vast portions of the Internet, has allowed us
to cut down on spam signifigantly.  The key to implementing this for us was
the ability to include a URL in SMTP 550 error messages directing the user
to a web site explaining why they were blocked and how to resolve.

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