[H-GEN] DNS and MTA setup [was: Key Mapping Problem (I think)]

[Greg Black]

On 2004-04-23, Rick Phillips wrote:

> Reply-To: rickp at suntech.net.au

I'm not sure why you put this header on your email and, although
it's considered bad form, I've decided not to honour it on the
grounds that you possibly don't understand its purpose and
because it's clear that at least one reader of this thread does
not understand the issues -- I suspect that many Humbug members
who try to run mail servers could benefit from some information.

OK, now to the problem.  As I hinted in my previous post, the
main thing is DNS, not MTA setup.

Let's consider this in two parts -- the delivery to Humbug and
the internal network processing.  On the current message, we see
the following:

> Received: from hegwig.suntech.net.au ([203.63.166.202])
> 	by caliburn.humbug.org.au with smtp (Exim 3.35 #1 (Debian))
> 	id 1BGf0f-0003VK-00
> 	for <general at lists.humbug.org.au>; Fri, 23 Apr 2004 00:17:01 +1000

And this is the previous equivalent header:

> Received: from hegwig.suntech.net.au ([203.63.166.202]
> 	helo=localhost.localdomain)
> 	by caliburn.humbug.org.au with smtp (Exim 3.35 #1 (Debian))
> 	id 1BGWlX-0001jj-00
> 	for <general at lists.humbug.org.au>; Thu, 22 Apr 2004 15:28:52 +1000

Note that the new header is missing the line about the HELO,
because we can presume that hegwig.suntech.net.au actually used
its own name in its HELO this time (as it should have done).  So
this part is now fixed.

Now, consider the internal header:

> Received: from unknown (HELO rick) (192.168.2.102)
> 	by 192.168.2.185 with SMTP; 22 Apr 2004 14:17:00 -0000

Compare it with the earlier one:

> Received: from unknown (HELO ?192.168.2.244?) (192.168.2.244)
> 	by 192.168.2.185 with SMTP; 22 Apr 2004 05:28:50 -0000

So, now we have 192.168.2.244 saying "HELO rick" rather than
just giving its IP; but that's equally useless.  The problem is
that the receiver looks up the IP address of the connecting host
in the DNS to see what its name is.  Since the DNS is either not
setup at all, or else is setup incorrectly, it finds no name for
192.168.2.244 and so it puts "unknown" in the Received header.

So what you need to do here is to setup your DNS so that when
192.168.2.185 looks up 192.168.2.244 it gets a sensible fully
qualified domain name for it.  If you don't care about domains
in general (although this would be a strange choice), you could
get by if you put the necessary data in /etc/hosts instead.

> Thanks for the lesson on this.  I have not found any reference to HELO
> addressing in the rather scanty Qmail manual I have so I have attempted to
> address this with the old Webmin standby.  I am always reluctant to use this
> as it has caused things to break for me in the past.  Please let me know if
> I have succeeded in changing to the correct HELO.

See above.  As for what to do about qmail's HELO, this is
answered fully in the qmail manual -- qmail-remote(8) in this
case.  If you can't understand that, let me know and I'll
provide extra information.

But, just to be clear, the issue here is not about qmail -- it's
about DNS.

Cheers, Greg
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