The emails sent to Exclaimer Cloud are not being delivered (or delivery is delayed), and the Microsoft 365 message trace shows the following error:
You received this error message because the Exclaimer proxy server is unable to identify the server to which the message needs to pass.
Typically, this scenario occurs when the Mail Routing options in Exclaimer Cloud are configured to return messages to the Sender Domain. The configuration implies that Exclaimer Cloud performs a lookup for each processed email, passing the processed email back to the server(s) specified within the sending domain name’s MX records.
Follow these steps to resolve the issue:
- Log into the Exclaimer portal (portal.exclaimer.com) and Launch your subscription.
- From the left-hand pane, click Configuration, then select Manage Mail Flow.
- In the right-hand pane, under Mail Routing Domain, are the relevant options.
- In Domain Name, enter the .omnicrosoft.com domain name - this can be located in the Domain list in the Microsoft 365 Admin Center. This setting is important, and an incorrect domain can result in mail flow issues.
- Click SAVE to save the changes made.
NOTES: The MX record for the Domain name (in the Mail Routing settings) should specify a single Exchange Online Server for your Microsoft 365 tenancy.
- To check the MX record for your own Domain name, use a DNS lookup tool, such as MXToolbox.
Example showing Exclaimer's domain: