Re: what controls received from address?

On Monday 22 Feb 2016 23:09:52 francis drake wrote:
> Hi all,
> 
> I have email that is being rejected by a mailserver with the following
> error:
> 
> Remote_host_said:_553_We_don't_accept_mails_from_MX_with_missing_DNS_A_or_PT
> R_RR

...

Your reverse lookup result for the MX machine is interesting,

> dnsq ANY 26.143.243.162.in-addr.arpa. a.ns.theorb.net.
> answer: 26.143.243.162.in-addr.arpa 3600 PTR 26.143.243.162.theorb.net

esp. note the numbers (IP number) encoded in the name... (see further down)

...

> The only place left to look is the Received header in the email itself:
> Received: from 127.0.0.1 (HELO a.mx.theorb.net) (162.243.143.26)
> 
> Could the rejection be because of the 127.0.0.1?

I'd be reasonably confident that's a red herring.

> If so, what settings in qmail must be changed to return the public IP?
> I've tried every control setting I could think of.

You've not told us anything about your config: Are you running via tcpserver 
etc, and potentially log entries around the failing incoming email may be 
helpful. Also details of the flavour of qmail/netqmail/patches etc. that you're 
running.
 
> I'm very confused.  There is only one server that rejects my mail and I'd
> like to cover all my bases to make sure my server is 100% compatible with
> everybody else's :D

I suspect that the remote system is giving an inaccurate error message, or 
that you hit a temporary fault.

The temporary fault scenario could be that the remote system is unable to 
successfully perform a reverse DNS lookup on the sending IP, but I presume 
this is an ongoing rather than a one-off problem, making that scenario unlikely

The inaccurate error message feels more likely - looking at the reverse DNS 
lookup I highlight above, the resulting PTR record includes the IP address 
within the name. PTR names like this are considered by some systems to be 
strong indicators of the sending system being a dynamic IP address, and 
therefore suspect (e.g. of being part of a botnet). In this case I suspect the 
receiving system acts with extreme prejudice towards such systems like yours; 
the error message given may actually include this scenario, even though it 
doesn't say so.

Possible solution: Talk to your provider to get the PTR record changed to 
something that looks more like a 'normal' DNS name. Bonus points for email 
purposes if it looks like the HELO/EHLO name used by the machine; also make 
sure that the name you use resolves to the machine's IP.

Please keep the list posted with your progress on this.

cheers,

Andrew.
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