[Mimedefang] Potential for Business mail servers to not havereverse DNS

[Joseph Brennan]

--On Friday, September 22, 2006 8:37 -0700 John Rudd <john at rudd.cc> wrote:

> * A PTR record for its IP address ("the connecting IP address").  Failure
> leads to a temporary rejection of the message.
> * The PTR record must resolve to a name which is they key for an A
> record.  Failure leads to a temporary rejection of the message.
> * The A record must have at least 1 IP address which matches the
> connecting IP address.  Failure leads to a permanent failure of the
> message.
> * The name from the PTR record must not look dynamic.  Failure is a
> permanent rejection of the message.
> * The above restrictions can be avoided via SMTP-AUTH.
>
>
> I have yet to find out that any such rejection was a valid email message.


I happen to be logging all missing RDNS, accepted or not.  Within 30
minutes we saw the following on one host of five.  The first 3 have no PTR. 

The other 2 have nonmatching forward and reverse.

IP			domain in the sender address (my comment)

192.165.223.234		reuters.com (news)
64.30.239.160		mailer-relay.sportsline.com (sports news)
206.220.211.195		indiaclub.com (online vendor)

57.66.153.130		weforum.org (nonprofit org)
64.39.15.8		lists.kabissa.org (nonprofit org)


Joseph Brennan
Columbia University Information Technology