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Non-Delivery Report: [550 5.7.350 Remote server returned message detected as spam]

  1. Exclaimer Knowledge Base
  2. Solutions
  3. Mail Flow
Payal Arya
  • Updated

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:

ERROR:550 5.7.350 Remote server returned message detected as spam -> 550 5.7.1 Recipient rejected (R1): 1487328208.37028.gmy2-mh822 [104.40.229.156] [Response from server]

DSN generated by:  MMXP123MB1230.GBRP123.PROD.OUTLOOK.COM
Remote server:  smtp.eu1.exclaimer.net

Reason

Typically, this scenario occurs if the Mail Routing option in Exclaimer is configured as Sender Domain. This configuration results in Exclaimer delivering the message to the server specified on the sending domain name’s MX records.

Resolution

We recommend: You change the Mail Routing options within your Exclaimer subscription to deliver the email directly back to Microsoft 365 (instead of the sender domain’s MX records).

Follow these steps to resolve the issue:

  1. Log into the Exclaimer portal (portal.exclaimer.com) and Launch your subscription.
     
  2. From the header bar, select the cogwheel icon to open the Settings menu.

  3. Select Mail Flow.


     
  4. Locate Mail Routing Domain. You may have to scroll.
     
  5. 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.

    Example: 
  6. 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: