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Possibly forged hostname

Posted on 2013-11-07
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Last Modified: 2016-07-11
I'm getting a rejected email from a specific domain only, the rejection message is: "451 4.1.8 Possibly forged hostname for 64.132.162.194 (in reply to RCPT TO command)".

I have only one exchanged server 2010 and barracuda at front. I have setup sendconnectors that the smarthost point to barracuda as a smarthost, under sendconnector network properties.

Domain records are at Register.com. 64.132.162.194 resolves to barracuda.trendsinternational.com and reverse records also resolves to barracuda.trendsinternational.com.

Again, there is only one customer rejecting, our emails.

thank you very much!
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Question by:paco1969
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Simon Butler (Sembee) earned 500 total points
ID: 39630361
If there is a problem, it is with the appliance, as that is what the external server will see.

Do the test as outlined here:
http://cbl.abuseat.org/helocheck.html

That will verify how your appliance is announcing itself to the world.

Simon.
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Author Comment

by:paco1969
ID: 39630528
Simon, thank you for your response. I have tried your suggestion and this is what I got back RCPT TO: helocheck@helocheck.abuseat.org
550 5.7.1 Unable to relay
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Author Comment

by:paco1969
ID: 39630541
Delivery has failed to these recipients or groups:

helocheck@helocheck.abuseat.org
A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.


and I got this from outlook: Generating server: barracuda.trendsinternational.com

helocheck@helocheck.abuseat.org
#< #5.0.0 X-Spam-&-Virus-Firewall; host helocheck.abuseat.org[54.245.112.115] said: 550 *** The HELO for IP address 64.132.162.194 was 'barracuda.trendsinternational.com' (valid syntax) *** (in reply to RCPT TO command)> #SMTP#
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LVL 63

Expert Comment

by:Simon Butler (Sembee)
ID: 39630648
The NDR is correct. If the host name is valid in the NDR and is what you expect then everything would appear to be correct - it has to be a false positive on the other side.

Simon.
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Author Comment

by:paco1969
ID: 39630921
Simon, an observation: when I check MX lookup for trendsinternational.com on MXToolBox I get: Pref            Hostname                                       IP                 Address       TTL       
         0          exchange.trendsinternational.com       64.132.162.194       24 hrs
       10          mail.trendsinternational.com       64.132.162.194       24 hrs       
Also, I want to thank you very much for your assistance.
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Assisted Solution

by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 500 total points
ID: 39630939
It would have to be a very picky site to reject on that basis. It would do no harm to replace the mail one with the actual host name and delete the 0 one completely.

Simon.
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Author Comment

by:paco1969
ID: 39631011
you mean replace it with the exchange host name or barracuda name?
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by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 500 total points
ID: 39631244
The appliance, because that is what the internet sees. Exchange is behind the appliance, but the internet doesn't care.

Simon.
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Author Comment

by:paco1969
ID: 39631263
Thank you simon, you have been a great help!!
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Expert Comment

by:Simon Butler (Sembee)
ID: 41704157
Object. I have answered the question.

ID: 39631244
ID: 39630939
ID: 39630361
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