delivery failures - host not found ?

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kthomas
Posts: 22
Joined: Sun Aug 27, 2006 2:59 pm
Location: Germany

delivery failures - host not found ?

Post by kthomas »

Hi,

I have a problem receiving mail from a certain mail server. I´m not sure if it concerns also other servers or only this one.
At work, I send a mail to my private account, for which Rollernet is configured as mail host (MX). Sometimes it works fine, but sometimes I get an error message from my employers mail server:

Code: Select all

The original message was received at Tue, 6 Oct 2009 08:50:19 GMT 
from uk-emamta003.ema.pwcinternal.com [10.250.44.242] 
 
   ----- The following addresses had permanent fatal errors ----- 
<username@mydomain.de> 
 
   ----- Transcript of session follows ----- 
550 5.1.2 <username@mydomain.de>... Host unknown (Name server: mail2.rollernet.us.: host not found) 
The username is in the recipient list, and I receive mails on that account - and some mails from my work address are delivered, too.
"mydomain" is kt 1.de, but I tried a few other domains I had configured for using RollerNet, and I think the name servers are set up correctly.

Most times, when I send the message again, it is delivered without errors.
The RollerNet log files don´t show any errors, the delivery failures are not logged.

Do you have any hint, what´s going wrong here ?

Thank you,
best regards

Karsten
Seth
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Location: Nevada
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Post by Seth »

From the error message, the server at 10.250.44.242 had a DNS problem and was unable to resolve mail2.rollernet.us. It's not appearing in our logs because it never left their server. I can only guess that the problem could be the server is using an unreliable DNS resolver or has connectivity issues. Without a "dig" trace or a similar tool that will show the steps the resolver made during the time it was failing it's hard to tell.

We have other TLD's besides the .us domain, I suppose I could set up something under .com and see if that works better for you.
Seth Mattinen, Roller Network LLC
kthomas
Posts: 22
Joined: Sun Aug 27, 2006 2:59 pm
Location: Germany

Post by kthomas »

Hi Seth,

thanks for your answer.

Since pwc.com is a very large company and the mail servers for Europe are located in UK, I think there is unfortunately no chance to discover anything e.g. by our IT service dept ... it would last a few months to escalate the topic. :roll: Maybe the servers are on full load, but - strange to say - my own (private) address is the only one the problem occurs with. No other external mail to our clients has been returned before.

As far as I understand the message, I think their server has no problem with my name server, as it reads the MX entry correctly.
Maybe we could try it with a .com domain, but I don´t know about the effort it creates ...
And I wonder if there are no other users with the same problem.

Best regards,

Karsten
Seth
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Post by Seth »

We have "rollernetwork.com" and I'll just create mail/mail2 A records under that. I'll need to distribute it to our internal nameservers, but it's not much effort.

As far as I know there are no other reports of this problem.
Seth Mattinen, Roller Network LLC
Seth
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Posts: 309
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Location: Nevada
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Post by Seth »

There's one other thing that just came to mind: IPv6. All of our nameservers that serve the domains like rollernet.us are dual-stack with IPv6 addresses. If they are IPv6 enabled and there's an intermittent problem with IPv6 connectivity, that could also cause a failure.

I can bring up an extra nameserver that only answers on IPv4, but that would take time.
Seth Mattinen, Roller Network LLC
kthomas
Posts: 22
Joined: Sun Aug 27, 2006 2:59 pm
Location: Germany

Post by kthomas »

Okay, I think it could be pretty difficult to figure it out ...

Maybe you are interested in doing some further tests, and I would be glad to assist you. Unfortunately I only can test it by sending mails, as I think I wouldn´t get an answer (on short notice) from our IT department asking for configuration details.

I wonder about caching. In case of a properly delivered mail our servers should have the correctly resolved DNS entries in cache, and the next delivery task shouldn´t fail. (Maybe they fail because of different mail servers with different caches ?) That brings me to the thought that only one of their servers is misconfigured, while others are correct - that would explain that some mails are delivered while others are not.

The problem occurs since a few months, but - as I see it´s not easy to figure out - I can live with the actual state, as it seems to be the only server the problem occurs with and meanwhile for my "internal" mail I can use another domain not using mail.rollernet.us.
I think you could be right with IPv6 - and I could imagine a sort of compatibility issue. And I´ll try to ask our IT dept if they have an idea.
kthomas
Posts: 22
Joined: Sun Aug 27, 2006 2:59 pm
Location: Germany

Post by kthomas »

hmm ... maybe it´s just fortune, but my last 10 mails were processed correctly, no errors occured anymore ! :D
If you didn´t reconfigure something, it seems that someone in our IT department installed an update ...
I´ll come back if it fails next time.

Thank you and best regards,

Karsten
Seth
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Posts: 309
Joined: Sun Aug 30, 2009 10:44 pm
Location: Nevada
Contact:

Post by Seth »

I haven't changed anything yet - I've been too busy physically moving all of the equipment to our new facility to do much of anything else.
Seth Mattinen, Roller Network LLC
kthomas
Posts: 22
Joined: Sun Aug 27, 2006 2:59 pm
Location: Germany

Post by kthomas »

I thought as much ...
Maybe someone of our IT read this thread and reconfigured his mail server :-)
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