Messages are identified as spam with NDR 550 5.7.350


Using Exclaimer Cloud, some message are rejected with a Non-Delivery Report/Receipt (NDR), similar to the example shown below:

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

DSN generated by:  MMXP123MB1230.GBRP123.PROD.OUTLOOK.COM
Remote server:


Typically, this scenario occurs if the Mail Routing options in Exclaimer Cloud are 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.


Configure Mail Routing options in Exclaimer Cloud to deliver the message back to Office 365, instead of the sender domain’s MX records. To do this, follow the steps below:

  1. Log into the Exclaimer portal (
  2. Click the Launch button for your subscription.
  3. Click the Settings button at the top of the page.
  4. Click the Mail Flow
  5. Click the Edit button under the Mail Routing
  6. Choose Static Domain from the drop-down list and then specify the Office 365 domain name (ending

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