[Mimedefang] Potential for Business mail servers to not have reverse DNS

Joseph Brennan brennan at columbia.edu
Fri Sep 22 08:47:51 EDT 2006

--On Friday, September 22, 2006 8:38 +0800 Mark van Proctor 
<m.vanproctor at acquire.com.au> wrote:

> Just wondering what the consensus is in regards to mail servers that do
> not have reverse DNS configured.
> Is it common for business mail servers to be unconfigured in this way?
> I have been watching my logs for a few days and all emails from mail
> servers that connect with an IP address that does not reverse DNS map
> have been spam.

It is not common, but there are enough of them to prevent us just
rejecting for this reason.  There are two usual cases.  One is a
small business or nonprofit with one system admin trying to do
everything and not being aware of the DNS record; those get fixed
when you tell them.  The other case has to do with a third party
hosting company or with some kind of firewall, and in those cases
the sys admin sometimes claims that fixing it is beyond his power.
But then sometimes they fix it.

We score for it, so sometimes other factors push the score to where
we reject.  That's why I've had some correspondence with various
people.  It has never been a large company with a real IT department.
It's always some small-scale operation.

Joseph Brennan
Columbia University Information Technology

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