How to Troubleshoot Exchange Server Error 451 4.4.0 DNS Query Failed?

There are numerous users across the globe who are facing issues while working on Exchange Online Server. One such error associated with the Exchange Server is 451 4.4.0 DNS query failed Exchange server error in message queues. Are you hunting for the solution to resolve Exchange Server error 451 4.4.0 DNS query failed issue? Then, you have reached the right blog where we will help you in resolving this error. So, read on and follow the steps sequentially to troubleshoot Exchange Server 2010 error 451 4.4.0 DNS query failed.

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Let’s follow the below-listed scenario,

“I am working with the hybrid setup with two Exchange Server 2016. The first server is at location A and the second one is at location B. While working, suddenly I encountered an error stating, Exchange server error 451 4.4.0 DNS query failed. the error was: SMTPSEND.DNS.NONEXISTENTDOMAIN DOMAIN.” I have tried different approaches with my level of understanding, but it did not work. Could someone address this query and help to get this resolved?”

“I have been working on Exchange Server since the time I have joined in this organization. Moreover, it is always a pleasure to work with Exchange Online Server. Recently, I conflicted with an error message and honestly speaking I am not aware of how this error occurred. It prompted an error message showing 451 4.4.0 DNS query failed. Kindly let me know with the solution to resolve 451 4.4.0 DNS query failed Exchange Server error in message queue issue. Looking forward to the earliest response.”

What Causes Exchange Server to Prompt 451 4.4.0 DNS Query Failed Error?

Most of the Exchange Server users have noticed that their emails are not getting delivered either to a particular or some other domain. Then, it is considered that Exchange Server 2010 error 451 4.4.0 DNS query failed has occurred. This error occurs when the system fails DNS lookup due to misconfiguration or sometimes the address has been manually blocked by the recipient domain. In order to resolve this 451 4.4.0 DNS query failed error, we need to fix the settings for specific remote domains and for all remote domains.

Exchange Server Error 451 4.4.0 DNS Query Failed Occurs While Sending Emails to Specific Remote Domains

The Exchange Server prompts this error message when the remote DNS servers ignore the respective query and revert back with an unexpected response.

In order to curb this issue, one needs to create send connectors for the infected remote domains. After that, configure the send connectors so that the remote domain can be used as the Mail Server as the smart host. For that, follow the below-stated steps in sequence,

1. Firstly for the affected remote domain, check the IP address of the MX record(Mail Server). For that, use NSLOOKUP or MX Record lookup tool
2. Now, create a new send connector for this remote domain. Therefore, it is important to configure the settings as described below,

• From the Address space section, add the infected remote domain. For instance, contoso.com

• Under Network settings option, choose Route mail through the following smart hosts radio button
• Then, enter the IP address of the MX record which was initially entered in step 1 and click OK

• After that, make the Configure smart host authentication settings to None and click the Next button

After this, the Exchange Server sends an email to this remote domain which will deviate the DNS query. After which, the Mail Server is connected in the remote domain using the IP address directly.

Exchange Server 451 4.4.0 DNS Query Failed Error Occurs While Sending Emails to All Remote Domains

In another case, the Exchange Server error 451 4.4.0 DNS query failed occurs when the DNS Server which the Exchange Server uses is not working or responding. Generally, Microsoft Exchange Server uses network adapter DNS settings by default for outgoing remote mail routing.

This 451 4.4.0 DNS query failed Exchange Server error in message queue can be fixed by resolving the issues which are associated with the local DNS server. For that, we need to configure the external DNS server for remote mail routing. To do the same, follow the below-listed steps,

• First of all, open the Properties page of the Exchange Server which hosts the send connector
• After that, under External DNS Lookups option, add the IP address of the public DNS Servers and click OK

• Then, from the Network section, select the checkbox for Use the external DNS lookup settings on servers with the transport roles option in the send connector which is responsible for remote mail routing

By configuring the above steps carefully, a user will no more face 451 4.4.0 DNS query failed error in Exchange Server.

Expert Method to Resolve Exchange Server 451 4.4.0 DNS Query Failed Error

If the above-discussed approach fails to repair 451 4.4.0 DNS query failed Exchange Server error in the message queue, then it is always recommended to switch to a third-party utility. For that, SysTools Exchange Recovery tool is the supreme solution to troubleshoot Exchange Server error 451 4.4.0 DNS query failed. It is developed with powerful algorithms to repair the Exchange Server mailbox items which help to resolve all the errors in the Exchange Online Server. This tool comes with a simple and friendly interface which ensures to resolve 451 4.4.0 DNS query failed error from the Exchange Server without causing any technical distrusts.

How to use Exchange Recovery Tool

Step 1: Download and launch SysTools Exchange Recovery.

Step 2: Add Exchange EDB file in the software.

Step 3: Preview and select files that need restoration.

Step 4: Choose the file format for saving and Export recovered data.

Let’s Sum Up

Microsoft Exchange Server is widely used across the globe which ensures to satisfy all the requirement with respect to the business needs. Thus, Exchange Server error 451 4.4.0 DNS query failed problem can stop the valued work causing disruption to the user. Though the manual method can be utilized, it requires proper technical knowledge. If the manual method fails to reconcile this issue, then go ahead with the finest expert method as discussed above.

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