Fix Email Delivery Issues for Error Code 550 5.1.10 in Exchange Server

Sometimes, when users try to send an email in your Exchange Server infrastructure, it bounces back with a non-delivery report (NDR) message, with the error code 5.1.10 SMTP; 550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup. As you can see, the error message says that the recipient is not found. There could be various reasons for this error message. In this post, we will help you to find out the causes of this error and the ways to fix it.

Ways to Fix the Error 550 5.1.10 in Exchange Server  

• The first thing to do is look at the occurrence of the message. Has the message been occurred to a particular user or to all users? Has the message been received when communicating with a particular email address or with all the domains? This will help you identify the cause of the issue and give you a clear indication if it’s a problem with one or all users.
• Check the user’s email and make sure that the email address is written correctly and with no spaces or special characters.
• You can also try to resend the message by clicking on the Send Again button in Outlook.

• Another thing to do is send a new message to the email address. This will ensure that there is no issue with the content of the message. To ensure that there isn’t a cached email address that could be malformed, send an email to the user by typing the entire email address manually. The last thing to check if any rules are configured in the mailbox. If any, disable them until a test is done.
• If the above ways fail, you need to look at the Exchange Server Setup for any forwarding rules set on the server. For this,
• Open the Exchange Admin Center (EAC).
• Click on mail flow.

• Untick all rules entries under rules section by unticking them from the left-hand side.
  
  

• Retry the message again from the user.
• You should also confirm that the accepted domain or the main domain configured is set to Authoritative. For this, click on accepted domains Under mail flow and confirm accordingly.

• You must also check that the domain is not set as Internal Relay or External Relay (see below).

• If the problem persists, trace back to what happened on the server – from when it was working to when it stopped. This can be done by checking the log of events on the server. It may happen that a Cumulative update is installed that has corrupted the configuration of the server, a third-party application or update is installed, antivirus rules or firewall rules are changed, or a simple human error.

• Another thing to do is check the MX records of the external domain of your Exchange Server. It’s not the first place that you would start with, but it’s always good to verify the records. A way to test is to log into the DNS hosting account and verify that the MX record is truly pointing to the Exchange Server. Usually, there would be an A Record with the name mail.mydomain.com pointing to the external IP address of the Exchange Server, and the MX record with the lowest priority pointing to the A record. There could be issues with the DNS hosting that would prevent emails to be delivered, if misconfigured or missing.

To Conclude

In cases where there is an issue with the Exchange Server and it needs to be re-installed due to a corrupted installation or the installation of a Cumulative Patch (CU) gone wrong, it is suggested to use an application, such as Stellar Converter for EDB. This EDB to PST Converter software can export all the data from your databases without data loss.

With Stellar Converter for EDB, you will be able to open multiple EDB files from any Exchange Server version. You don’t need an online Exchange Server to extract data from your Exchange Server databases. The software offers a clean and familiar Outlook-like interface where you can see the whole structure of your database, along with a full HTML viewer and in-line search. You can granularly export mailboxes, shared mailboxes, disabled mailboxes, and public folders to PST and other formats, such as EML, HTML, PDF, and MSG.

With Stellar Converter for EDB, you can export directly to an online Exchange Server database. In case the Exchange Server is rebuilt, you can easily open the EDB files and export directly to a brand-new database with ease, with manual or automatic mailbox matching. You can export from any version of the Exchange Server database to any Exchange Server version. Other features include VIP (preference) exporting where mailboxes of your choice will be exported first, parallel export to process a few mailboxes at once, and the ability to continue the export if the application is interrupted in any way. You can also use it as a migration tool to migrate to Office 365 tenants.

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About The Author

Ravi Singh

Ravi Singh is a Senior Writer at Stellar®. He is an expert Tech Explainer, IoT enthusiast, and a passionate nerd with over 7 years of experience in technical writing. He writes about Microsoft Exchange, Microsoft 365, Email Migration, Linux, Windows, Mac, DIY Tech, and Smart Home. Ravi spends most of his weekends working with IoT (DIY Smart Home) devices and playing Overwatch. He is also a solo traveler who loves hiking and exploring new trails.