Zen Internet Support Forum

We've got an exchange server, hosted on a Zen connection, and randomly, users get the above error when sending emails. I've inserted 555 in the email addresses to (hopefully) prevent spamming

 Generating server: diamond.cor.local

Support@rhombus-systems.com555
smarthost03.mail.zen.net.uk #550 Envelope Sender: Domain must resolve in DNS! ##

Original message headers:

Received: from diamond.cor.local ([10.1.0.4]) by diamond.cor.local
 ([10.1.0.4]) with mapi; Thu, 17 Jul 2008 09:08:18 +0100
From: NOC Office office@thenoc.org.uk555
To: 'Rhombus Support' Support@rhombus-systems.com555
Date: Thu, 17 Jul 2008 09:08:17 +0100
Subject: FW: RE: done it
Thread-Topic: RE: done it
Thread-Index: Acjnh1ORFScC20oGSIOadCz+7haQ7wAXG6vQAAAKZCoAAAJaAA==
Message-ID: <820CEEA531DF294FA9BF33478B68A700099B04734D@diamond.cor.local>
Accept-Language: en-US, en-GB
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: en-US, en-GB
Content-Type: multipart/alternative;
	boundary="_000_820CEEA531DF294FA9BF33478B68A700099B04734Ddiamondcorloc_"
MIME-Version: 1.0

 This has been happening for a few months, but it seems to be getting worse. Sometimes, resending the email works fine, and it gets through. Other times, a string of these undeliverables appears. I believed I'd tracked the problem to having the sending domain name hosted with 123-reg - so yesterday I transferred it to Zen. Still the same problem.

 Any help would be appreciated!

This is a result of Sender Address Verification being periodically unable to find the mail server for the the thenoc.org.uk domain;

#host -tmx thenoc.org.uk
thenoc.org.uk mail is handled by 10 mailex.mirfield.org.uk.

#host mailex.mirfield.org.uk.
mailex.mirfield.org.uk has address 88.96.41.54

hmmmm worked...ok try again

#host mailex.mirfield.org.uk.
Host mailex.mirfield.org.uk not found: 3(NXDOMAIN)

 

On closer inspection the mirfield.org.uk doesn't have a record for mailex on ns0.zen.co.uk or ns1.zen.co.uk.  Hence it's failure to resolve, it would seem out resolving DNS platform has one server with an old record which is why it responded with one the first time.  mirfield.org.uk will need to add a record for mailex or thenoc.org.uk will need to update their MX to point to a FQDN which resolves.

 

 

 

Thanks for the reply - the mailex record was set up correctly until yesterday, when I foolishly didn't add the A record for it when I transferred mirfield.org.uk over to Zen. I've added it, and hopefully this will solve the problem.

I really appreciate your help on this - I'd emailed Zen Technical Support ([1932600:2015192]) - you may be interested to read the conversation I had with your colleague!

 

Glad we found a resolution.  I'll look into your concerns regarding the ticket you raised with support.