When deploying Defend to Microsoft 365, there are potential issues that may arise. These issues can prevent Defend from functioning correctly, leading to email delays or failures. It is essential to troubleshoot these issues promptly and efficiently to ensure successful deployment.

This article highlights the common issues that may occur when deploying Defend to Microsoft 365 and how to manage them.

Mail Flow Issues 

This issue occurs when there is a problem with the mail flow in Microsoft 365 at the time of the Defend deployment. This deployment may cause significant problems with correctly processing emails, resulting in a blocked mail flow to your organization.

Resolution 

To resolve this issue, check the mail flow configuration in Microsoft 365 to ensure it is correct. Verify that your mail flow rules are configured correctly and that there are no issues with email transport. Rerun the health check on the Defend console's Settings page to ensure that the issue is resolved. If the issue persists, contact support for further assistance.

Email in Quarantine

This issue occurs when an email is being held in the Microsoft 365 quarantine before it has been processed by Defend, preventing Defend from processing it correctly. This issue can cause delays in email delivery and may also prevent Defend from correctly detecting phishing emails. 

Resolution 

To resolve this issue, check the quarantine settings in Microsoft 365 Defender to ensure they are configured correctly. Release any legitimate emails from quarantine and ensure that the quarantine settings are not blocking future emails unnecessarily. Rerun the health check on the Defend console's Settings page to ensure that the issue is resolved. If the issue persists, contact support for further assistance.  

Unknown Errors 

These issues occur when an unknown error is encountered during the Defend deployment or the health check process. This issue may impact Defend's ability to process emails. 

Resolution 

To resolve this issue, gather more information about the error by checking Microsoft 365 event logs. Look for any error messages or codes that may indicate the cause of the issue. Then, contact support for further assistance, providing as much detail as possible about the error. Rerun the health check on the Defend console's Settings page to ensure that the issue is resolved.