Fix Exchange SMTP Error 550 5.7.1 Unable to Relay

Working with Exchange Server itself is a challenge!

With vast number of facilities in data management and exchange, there come responsibilities to handle multiple errors which can appear anytime in front of you. We are going to discuss one such common Exchange error – “Exchange SMTP Error 550 5.7.1 Unable to Relay” which is haunting the Exchange administrators for long. In this article, you will find some native approaches to fix the error while discussing about the nature and causes of this SMTP error in detail. Let us read this blog carefully.

What is Exchange SMTP Error 550 5.7.1 Unable to Relay? When and how it occurs?

Exchange SMTP Error 550 5.7.1 Unable to Relay usually indicates certain cryptic error codes by the HTTP Protocol meant to restrict emails from sending between Exchange Server and its client application. This message is basically a non-delivery report of emails relay by the Microsoft Exchange Server. This error occurs when the Exchange user or administrator is trying to send emails between Exchange client and server and the recipient has not enabled the relay feature. It restricts any email transfer between the server and client due to message relay and come up with an error message resembling delivery failure of emails. There is another chance of Exchange Server sending commercial emails along with remote domain sending unsolicited emails information while encountering this error.

The message display is as follows:

Error Message:
System Administrator
Your message did not reach some or all of the intended recipients.
The following recipient(s) could not be reached:
550 5.7.1 Unable to relay for

Common indications of the Exchange SMTP Error “Unable to Relay” are:

  • Send/Receive failure of the emails displaying error code 5.7.1, 5.0.0 or 5.7.3
  • With constant increase in domain counts, occurrence of error message
  • Sending of commercial email messages through Exchange Server while remote domain will send unsolicited commercial emails information received through the Exchange system

The user should know the possible reasons behind this SMTP error to get back to the normal exchange of email messages between the Exchange Server and Client. Read out the causes for this troublesome SMTP error in the below-stated points.

  • SMTP authentication failure for the respective sender domain
  • Outgoing Mail Server fails to recognize the sender address
  • Restrictions on sender domain defined by the receiver domain under Recipient’s policy
  • Email message was routed to the incorrect email server
  • Email sent to a big number of recipients or distribution group
  • Exchange Server Database is corrupted

Learn Manual Fixes for Exchange SMTP Error 550 5.7.1 Unable to Relay

With the Exchange Server Manager, Exchange administrators can settle or fix this SMTP error as they can manually choose and assign the IP address and domain name which they want to relay from the default SMTP Virtual Server. It may help the sender domain authentication as well as in recognizing the sender address.

Please note that this manual approach is applicable for the Microsoft Exchange 2010 and above versions only.

Using Exchange Server Manager to Fix Exchange SMTP Error 550 5.7.1 Unable to Relay

Exchange administrators or users with assigned administrator rights need to perform the following steps in the given sequence to fix “Exchange SMTP Error 550 5.7.1 Unable to Relay issue”.

  1. Start your Exchange system (on which Exchange Server is installed) and launch the Exchange Server Manager on it.
  2. On the left panel of the page, go to the Administrative Groups section.
  3. Under the Administrative Groups section, navigate to the Administrative Group Name>>Server>>Server Name.
  4. Under your Server Name, click Protocols option and then select SMTP option.
  5. Now, right-click on the Default SMTP Virtual Server option and click on Properties option from the list.
  6. Next, click on the Access tab, click on the Relay option and choose Only The List Below option.
  7. Select the IP address and Domain name for relay purpose. Select the checkbox saying “Allow all the systems to successfully authenticate to relay regardless of the list above”. Click OK.
  8. Finally, closed all the opened tabs and Exchange Server Manager.
  9. Try to send the emails now and check if this SMTP Error is eliminated or not.
    Note: Exchange administrators can also check the Exchange SMTP Error detail in the Application Event Log and perform the provided solution online from there. Or, can directly contact the recipient and inform him about the issue and seek solutions from their end.

The above approach can handle your issue of failure in email delivery. But, if the cause is something else and not the wrong authentication or restricted Recipient Policy, then you need to be more cautious here. If this solution does not get well for you, then remember one more reason for this error is mentioned at the start of this blog which is the corrupted Exchange Server database. Corruption in an Exchange database could be due to many factors such as virus infections, incorrect modifications in database schema, objects, intermittent power-supply, and sudden shutdown of system, interference of other installed programs like Firewalls or Anti-virus or more other factors. There could be many issues with a corrupted Exchange database which results in different errors one of which could be this Exchange SMTP Error 550 Unable to Relay. So, there is an utmost need to repair the corrupted Exchange database for normal functioning of the Exchange Server.

In-Built Repair Utility – Eseutil by Microsoft Exchange Server

Exchange Server has an in-built utility namely Eseutil for soft and hard Exchange database recovery, available at the Exchange system location

C:\Program Files\Microsoft\Exchange Server\V15\Bin

which can be used to defragment Exchange database, checking its integrity, repairing the corrupted database and also to reduce Exchange database size.

The basic command for repairing the corrupt Exchange database is – eseutil /p <location of the database>

Before running any command on the Eseutil application, it is strongly recommended to have a backup of your Exchange database file as manual way to repair Exchange database file can lead to loss of data during the repair process. One more drawback of this solution is this method is not suitable for large-sized Exchange database files as well as files with high intensity of corruptions. Also, users need to first dismount the Exchange database to run these commands on it and hence, it remains inaccessible at that time.

To deal with highly corrupted Exchange database files, we recommend you to opt for a reliable third-party tool. Exchange Server Recovery tool is an efficient tool with highly advanced programming and quite simple designed user-interface. It helps users to repair Exchange database with any sort of corruption level in few steps and fix different Exchange errors simultaneously. Users can choose the Exchange data owing to multiple smart filters and options integrated in the tool’s interface. The tool does not require much technical knowledge and can be run by all users because of the interactive user interface and features. The tool does not impose any restrictions on the Exchange Server rather support almost all versions of Exchange Server for complete data recovery and errors fixing. Before buying this tool, we advise you to know well about its features through its demo version available at the site.

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About Vineet Bhatt

Vineet has written on QuickBooks, Sage50, MySQL Database, Active Directory, email recovery, Microsoft365, Pattern Recognition and Machine learning. He is passionate about researching, exploring new technologies and creating interesting technical blogs to help organizations or database administrators solve multiple problems.

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