Scenario
You have configured Exclaimer for your Microsoft 365 tenancy and you notice some messages are rejected with a Non-Delivery Report (NDR), similar to the example shown below:
Reason
Typically, this scenario occurs where multiple hosts are configured for an MX record. Occasionally, Microsoft may change the MX record associated with your default domain while undertaking maintenance.
Resolution
Follow these steps to resolve the issue:
- Log into the Exclaimer portal (portal.exclaimer.com) and Launch your subscription.
- From the header bar, select the cogwheel icon to open the Settings menu, then select Mail Flow.
- In the pane, under Mail Routing Domain, are the relevant options.
- In Domain Name, enter the Microsoft 365 domain name with a single host. This setting is important, and an incorrect domain can result in mail flow issues.
- Click SAVE to save the changes made.