Subject: Re: MTAmark (was: Reality check please)

From: Peter Koch <[email-masked]>
Date: Wed, 16 Jun 2004 22:07:08 +0200

Markus Stumpf wrote:

> I am currently trying to contact people in DE. Peter Koch who is doing
> the monthly DNS host count for DE domains is willing to add a check for
> MX hosts and will provide information about the number of unique (based
> on IP address) MX server used for DE domains.

starting with 11291065 MX RRs coming out of this month's DE hostcount (see
http://www.TechFak.Uni-Bielefeld.DE/~pk/dns/hostcount/latest.html or
http://www.ripe.net/ripencc/pub-services/stats/hostcount/ for information on
what it is and how it works), the individual MX targets were identified,
bogus ones deleted and the remaining ones were fed a resolver to find the
number of unique IP addresses:

	11291065 MX RRs
	 7600000 ~ number of 2nd level DE domains
		 <http://www.denic.de/en/domains/statistiken/>
	 1058962 unique MX RR targets
	 1057546 valid MX RR targets (no '.', IP addresses, ...)
	  146224 unique IP addresses after resolving MX RR target names
	  144582 non-bogus IP adresses (ignoring RFC 1918 addresses,
		 unallocated address space, multicast, ...)
Some remarks:

  o Targets may reside both inside and outside DE.
  o Some larger address space holders ("class B", universities etc) tend
    to define MX RRs for almost all of their systems/addresses, sometimes
    including dialin lines etc. Since MX is inbound only this may have an
    adverse effect on the guesstimate for the proposal mentioned in the
    subject line.
  o The 144582 addresses belong to 26552 /24 address ranges.
  o Approx. 75% of the addresses identified do have a working reverse
    mapping (lead to one or more PTR RRs), the rest either yields NXDOMAIN
    or has resolving problems (timeout, SERVFAIL). For NXDOMAIN I didn't
    further differentiate 'not delegated' vs. 'not named in zone'.
  o Viewing /24 zones (and ignoring RFC 2317 for the sake of simplicity)
    80% of the /24's covered by the IP addresses found do have a working
    reverse mapping.

So, this is just the data, I'm taking no position whether or not these
figures can be used to calculate/estimate the number or percentage of
``legitimate'' outbound SMTP clients.

-Peter