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I am sorry for the delay. I had an personal emergency. I checked the destination MX and was not getting resolved and I could not telnet to them. It ended up being a mimecast issue. Thank you for your help.
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I am sorry for the delay. I had an personal emergency. I checked the destination MX and was not getting resolved and I could not telnet to them. It ended up being a mimecast issue. Thank you for your help.

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We are getting the error message in our queue for what looks like two domains but no others<br />
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&nbsp;&quot;451 4.4.0 primary target IP address responded with &quot;421.4.4.2 unable to connect.&quot;attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed to all alternate hosts.&quot;<br />
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We have an Exchange 2010 server and we have not made any changes recently and email flow has been okay otherwise. &nbsp; <br />
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The rest of our clients are okay. Is it on their end? Any assistance offered would be greatly appreciated.
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We are getting the error message in our queue for what looks like two domains but no others

 "451 4.4.0 primary target IP address responded with "421.4.4.2 unable to connect."attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed to all alternate hosts."

We have an Exchange 2010 server and we have not made any changes recently and email flow has been okay otherwise.   

The rest of our clients are okay. Is it on their end? Any assistance offered would be greatly appreciated.

451 4.4.0 primary target IP address responded with &quot;421.4.4.2 unable to connect.&quot;attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed

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.

Networking is the process of connecting computing devices, peripherals and terminals together through a system that uses wiring, cabling or radio waves that enable their users to communicate, share information and interact over distances. Often associated are issues regarding operating systems, hardware and equipment, cloud and virtual networking, protocols, architecture, storage and management.

451 4.4.0 primary target IP address responded with &quot;421.4.4.2 unable to connect.&quot;attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed

451 4.4.0 primary target IP address responded with "421.4.4.2 unable to connect."attempted failover to alternate host, but that did not succeed.Either there are no alternate hosts, or delivery failed