* Forwarded (from: personal) by mark lewis using timEd/2 1.10.y2k+.
* Originally from waldo kitty (1:3634/1000) to mark lewis (1:3634/12).
* Original dated: Tue Mar 17, 13:24

-------- Forwarded Message --------
Subject: Re: [Weasel] 450 Errors In Weasel Pro
Date: Mon, 16 Mar 2015 19:14:23 +1100
From: Peter Moylan 
Reply-To: weasel-list@os2voice.org
To: weasel-list@os2voice.org

On 16/03/15 16:46, Steven Levine wrote:
> In <550664ED.9020001@pmoylan.org>, on 03/16/15
>     at 04:06 PM, Peter Moylan  said:
>
> Hi Peter,
>
>> The "return path not verifiable" usually means that the receiving server
>> is trying to check that the claimed sender's address is a genuine mail
>> account. Typically it does this by starting a "send mail" transaction to
>> the address named in the MAIL FROM command, but aborting it before
>> actually sending anything. If this attempt fails, it concludes that the
>> send in the MAIL FROM command is a fake.
>
> Is this still true for a significant number of today's MTAs?  I was under
> the impression that these days most use SPF or one of its successors.

I don't know how common each method is, but the wording "return path not
verifiable" seems to me to point to a test of the return path rather
than an SPF check.

>> In this case, though, it appears to be checking the _recipient's_
>> address (robert.wolfe@winserver.us), and discovering that winserver.us
>> will not accept mail for robert.wolfe.
>
> I don't read it this way.  As I read the logs, it is the comcast
> mailserver that is rejecting the MAIL FROM with a 450.
>
> Reading between the lines, the MAIL FROM is foo@os2bbs.org and the RCPT TO
> is robert.wolfe@winserver.us.

Thanks, I missed seeing that. In that case I think I know what the
problem is -- see below.

>> Maybe we need to see a longer section of the log to work this out.
>
> We also need to know what the senders MX record looks like.  If we assume
> that mail.os2bbs.org is the mx then the reject make sense if the comcast
> mail server does SPF validation.

Here's the problem, as I see it:

[D:\Dev4\NumAnaly]nslookup -type=MX os2bbs.org
Server:  RTA1046VW.home
Address:  192.168.1.1

Non-authoritative answer:
os2bbs.org      preference = 0, mail exchanger = mail.os2bbs.org

Authoritative answers can be found from:
mail.os2bbs.org internet address = 50.194.33.5

[D:\Dev4\NumAnaly]nslookup 50.194.33.15
Server:  RTA1046VW.home
Address:  192.168.1.1

Name:    50-194-33-15-static.hfc.comcastbusiness.net
Address:  50.194.33.15

The problem is that the hostname
50-194-33-15-static.hfc.comcastbusiness.net does not match os2bbs.org. I
used to run into similar problems before I configured Weasel to use my
ISP's mail server as a backup relay.

There are two possible solutions:

(a) Convince comcastbusiness.net to put something into their nameserver
to map 50.194.33.15 to os2bbs.org. Some ISPs will do this for you.
Others will charge you for a static IP address but not follow through on
the nameserver implications.

(b) Configure Weasel to use a relay server as backup, to handle the mail
that is rejected because of the reverse DNS lookup problem.

-- 
Peter Moylan        peter@pmoylan.org       http://www.pmoylan.org

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 * Origin:  (1:3634/12)