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Where are you seeing this error? &nbsp;In an NDR? &nbsp;Try sending directly to the internet and bypass the smarthost for now.
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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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in the exchange message queue. I'm not great with exchange
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in the exchange message queue. I'm not great with exchange

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I kind of want to use the smarthost as i have been though
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I kind of want to use the smarthost as i have been though

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As a test then to isolate the issue.
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worked fine... <br />
<br />
But I have 50 email in the queue with the smarthost still.
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worked fine...

But I have 50 email in the queue with the smarthost still.

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oh... they just all started sending.. &nbsp;should i be using a smarthost? what does it help with ?
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oh... they just all started sending..  should i be using a smarthost? what does it help with ?

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You don't <b>need </b>a smarthost but they do have a benefit:<br />
<br />
<a href="https://en.wikipedia.org/wiki/Smart_host" rel="ugc">https://en.wikipedia.org/wiki/Smart_host</a><br />
<br />
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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You don't need a smarthost but they do have a benefit:

https://en.wikipedia.org/wiki/Smart_host [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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Legend.. thanks for your help.
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Glad I could help. &nbsp;Take care :)
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<div class="content wysiwyg-content">
I'm getting 451.4.4.0 dns query failed. The error was: DNS query failed with error ServerFailure<br />
<br />
Nothing has changed from my server which is strange. i use a smart host to route my email.<br />
<br />
please help .
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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 .

Exchange 2016 : 451.4.4.0 dns query failed exchange

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.