Date:  Fri, 6 Jun 2008 10:32:29 -0700
From:  "Jim Scott" <jscott (at mark) infoconex.com>
Subject:  [coba-e:13184] Re: Another Strange Sendmail Error
To:  <coba-e (at mark) bluequartz.org>
Message-Id:  <02ed01c8c7fb$4bd1ab90$0569a8c0@WORK1>
References:  <170727.10575.qm (at mark) web65613.mail.ac4.yahoo.com>
X-Mail-Count: 13184


>>
>> > Return-Path: <rebecka.davie (at mark) mayr-glatzl.at>
>> > Received: from 63-138-182-110.customer.static.ip.paetec.net
>> > (63-138-182-110.customer.static.ip.paetec.net [63.138.182.110] (may be
>> > forged))
>> > by [my server] (8.13.1/8.13.1) with ESMTP id m55EcXDE022327
>> > for <me (at mark) example.com>; Thu, 5 Jun 2008 09:38:37 -0500
>>

Ok I think I have your answer. The IP address 63.138.182.110 has a reverse 
DNS entry of 63-138-182-110.customer.static.ip.paetec.net

However if you do a A lookup on 63-138-182-110.customer.static.ip.paetec.net 
it does not resolve to anything. When that happens sendmail writes out (may 
be forged) and at that point will not use the DNS information in determining 
if it should block but instead will use only the IP address.

This makes sense since I can set my reverse DNS if I own the IP block to 
anything I want.

Here is a reference that talks about (may be forged ) and how if it fails it 
will ignore DNS and only use IP information.

http://www.sendmail.org/~ca/email/relayingdenied.html#MSGFORGED