Incoming emails from a specific domain are being sent to the Microsoft 365 quarantine or the user’s junk folders. This domain block is occurring across all Microsoft 365 tenants. It can be very frustrating if you send emails to customers whose mail is hosted on Microsoft 365, only for those messages to end up marked as spam. This situation negatively affects every business. In this article, you will learn how to fix the domain block in Microsoft 365 because of its reputation.
Find message in Quarantine or Message Trace#
Sign in to Exchange admin center and find the message using the Message Trace or Quarantine page. In this example, we will open the message from the Quarantine page.
Click on the message, and the details appear. It shows that the message was blocked because of the detection technology Domain reputation.
The DMARC, DKIM, SPF, and Composite authentication checks for the sender domain all appear as Pass.
Looking more into the details clearly shows that everything is correctly configured for the sender domain, and the message should not be blocked by Microsoft.
So, what is the solution to this problem, and how do we fix the domain from being blocked in Microsoft 365?
Submit message to Microsoft for review#
You must first submit the message to Microsoft for review by following the steps below:
- Click on the three dots (…).
- Click Submit for review.
- Ensure the email network message ID appears.
- Ensure that the recipient who had the issue appears.
- Select I’ve confirmed it’s clean.
- Click Next.
- Click Submit.
- Go to the Report Submissons page.
- Select the reported message.
- Verify that the results show No threats found.
- Copy the Submission ID.
- Open a support request in the Microsoft 365 admin center and add the copied submission ID to it. Ensure you direct the engineer to forward this support request to the Microsoft Defender team so they can see what is going wrong.
- The Microsoft Defender team will remove the domain from Microsoft’s block list.
That’s it!
Conclusion#
You learned how to fix a domain reputation block in Microsoft 365. It is important to know that domains can be blocked, and not only IP addresses, by the Microsoft Defender team. In fact, the blocking is mostly done by their AI system.
Submit the message to Microsoft for review, so they will analyze it and provide a result. However, this process does not automatically remove the domain from the block list. As a result, you must open a support request for the Microsoft team to manually remove the domain from the block list.
[!NOTE] All credits for this article goes to Ali Tajran. I recently had this issue and ran through this exact process, but this incident happened so long ago that I am unable to grab the proper screenshots.
