As an Exchange administrator, you may occasionally come across a situation where in a particular mail account on your Exchange server is unable to send mails to a specific domain. The Exchange user receives a Server error: '550 5.7.1 Unable to relay'. This generally happens when you try to send mails to addresses that are outside the domain of your company or organization.

Mail Relay generally happens when you connect to a mail server on one domain and try to send mails using another server on an external domain. This error signals that the outgoing mail server is unable to recognize you and hence, won't allow you to send mails. Another possible reason may be that there is no recipient policy for the expected domain in your organization.

In order to resolve server error 550, you need to verify certain things:

There are many possibilities that could be lingering the error. One of the most frequent reasons is corruption of the user mailbox. If you encounter any corruption in your Exchange database, use Stellar Repair for Exchange. The software is equipped with dedicated algorithms to repair corrupt Exchange databases and perform a safe restoration of all user mailboxes. The tool implements a simple, streamlined procedure to accomplish Exchange database recovery as described below:

Our Exchange Recovery software supports recovery of databases created in MS Exchange 2019, 2016, 2013, 2010, 2007, 2003, 2000, and 5.5. Moreover, it is compatible with Windows 10, 8, Windows 7, Vista, XP, and Windows Server 2012 and 2008.