[Mimedefang] Potential for Business mail servers to not havereverse DNS
brennan at columbia.edu
Fri Sep 22 12:11:11 EDT 2006
--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
> * 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)
188.8.131.52 reuters.com (news)
184.108.40.206 mailer-relay.sportsline.com (sports news)
220.127.116.11 indiaclub.com (online vendor)
18.104.22.168 weforum.org (nonprofit org)
22.214.171.124 lists.kabissa.org (nonprofit org)
Columbia University Information Technology
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