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We use Kerio 6.7.1 build 7695 and in this instance Outlook 2007...

Looking through the mail logs today I noticed that the same address was coming up repeatedly.

I found the user who sent the message and they say they sent it once, however the logs tell another story...

The first mail goes out...
[01/Oct/2009 10:19:48] Recv: Queue-ID: 4ac47434-0007d94f, Service: SMTP, From: <user<_a.t_>>, To: <somebody<_a.t_>>, Size: 10802, Sender-Host: 192.168.x.x, SSL: yes

Then it goes again...
[01/Oct/2009 10:19:49] Recv: Queue-ID: 4ac47435-0007d952, Service: SMTP, From: <user<_a.t_>>, To: <somebody<_a.t_>>, Size: 13338, Sender-Host:, SSL: yes

This then repeats every 2 seconds until it has fired out 100 messages.
I notice that the first send has the 'sender host' IP address of the genuine user and the other 99 use loopback.

The final log entry is:
[01/Oct/2009 10:23:09] Sent: Queue-ID: 4ac474fb-0007da49, Recipient: <somebody<_a.t_>>, Result: failed, Status: 5.3.2 554 5.0.0 Too many hops (101, max 100), message looping

What has gone on here?


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You e-mail configuration is creating an e-mail loop. This can happen:

  • when the MX record of the recipient domain points to your server
  • a user have setup a rule that automatically forwards or replies to mails and the recipient has also such a rule

On the KMS server, use nslookup to find the MX record of Does it point to your server?

Check if user<_a.t_> or somebody<_a.t_> have any rules setup.

Also check if is configured as domain in your KMS (shouldn't be).

[Updated on: Thu, 01 October 2009 14:31]

Dexion AG - The Blackberry Specialists in Switzerland

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Thanks for the response.

nslookup on our mail server gives me an IP, and it isn't our server.

I tried a mail server test with this IP on and got a 'no response' result. A quick port scan shows only port 80 as open on their server.

Putting their domain into MXToolbox retruns their MX record as being - nice.

Going directly to their domain on the web goes to one of those crappy holding pages with lots of search suggestions on it.

So to sum up, Kerio working fine and some server administrator somewhere is a complete an utter arse! Laughing

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I'm glad our tools were able to help. I've seen a lot of MX Records in my day, but I've never seen anybody set theirs to before.

We're planning on adding some tool tips to the results to help explain what they mean and how to interpret them. Based on this example, I think I'll put a check on the MX record results to show a big warning flag for any results returning private IP addresses, especially the loopback address.

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