You have configured Exclaimer Cloud for your Microsoft 365 tenancy and you notice some messages are rejected with a Non-Delivery Report (NDR), similar to the example shown below:
ERROR: 550 5.7.350 Remote server returned message detected as spam -> 550 5.7.1 Recipient rejected (R1): 1487328208.37028.gmy2-mh822 [22.214.171.124] [Response from server]
DSN generated by: MMXP123MB1230.GBRP123.PROD.OUTLOOK.COM
Remote server: smtp.eu1.exclaimer.net
Typically, this scenario occurs if the Mail Routing option in Exclaimer Cloud is configured as Sender Domain. This configuration results in Exclaimer Cloud delivering the message to the server specified on the sending domain name’s MX records.
We recommend: You change the Mail Routing options within your Exclaimer Cloud subscription to deliver the email directly back to Microsoft 365 (instead of the sender domain’s MX records).
The steps described below are from the old UI.
Follow these steps to resolve the issue:
- Log into the Exclaimer portal (portal.exclaimer.com) and Launch your subscription.
- Click on the options list from the top-right of your screen and select Settings.
- The Settings window is displayed, select the Mail Flow tab.
- Click the Edit button under the Mail Routing.
- From the Mail routing mode drop-down, select Static Domain.
- In Domain name, enter the Microsoft 365 domain name (ending in .onmicrosoft.com).
NOTE: 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 MX Toolbox.
- Click Save to save the changes.