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Exchange 2016 : 451.4.4.0 dns query failed exchange

I'm getting 451.4.4.0 dns query failed. The error was: DNS query failed with error ServerFailure

Nothing has changed from my server which is strange. i use a smart host to route my email.

please help .
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Jack 50
Asked:
Jack 50
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1 Solution
 
Jason CrawfordExchange EngineerCommented:
Where are you seeing this error?  In an NDR?  Try sending directly to the internet and bypass the smarthost for now.
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Jack 50Author Commented:
in the exchange message queue. I'm not great with exchange
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Jason CrawfordExchange EngineerCommented:
Gotcha ok no problem.  Here is a Technet article explaining how to configure a Send Connector to route directly to the internet.  You can either create a new SC and disable the current one or just modify the settings of the current Send Connector:

https://technet.microsoft.com/en-us/library/jj657457(v=exchg.160).aspx
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Jack 50Author Commented:
I kind of want to use the smarthost as i have been though
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Jason CrawfordExchange EngineerCommented:
As a test then to isolate the issue.
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Jack 50Author Commented:
worked fine...

But I have 50 email in the queue with the smarthost still.
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Jack 50Author Commented:
oh... they just all started sending..  should i be using a smarthost? what does it help with ?
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Jason CrawfordExchange EngineerCommented:
You don't need a smarthost but they do have a benefit:

https://en.wikipedia.org/wiki/Smart_host

Ultimately you'll want to verify the outbound smarthost name from the vendor because it appears they aren't accepting email from your Exchange server.
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Jack 50Author Commented:
Legend.. thanks for your help.
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Jason CrawfordExchange EngineerCommented:
Glad I could help.  Take care :)
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