If you are getting a non-delivery report with error code 5.1.8 and the following text: "Delivery not authorized, message refused" from Microsoft while sending emails, it is possible that you are added to the restricted users page in Microsoft 365 Defender Portal.
This can happen if you exceed the sending limit or get flagged by Microsoft’s spam filters. You will be restricted from sending email, but can still receive email. Salesflare has quota limits in place to avoid going over the email quota of your mailbox, but there are situations where this can happen.
However, removing a user from the restricted list in Microsoft 365 is a straightforward process. By following the below steps, you can easily unblock a user (or yourself) and restore access to the services that were previously restricted.
Step 1: Sign in to the Microsoft 365 Defender portal
Go to the Microsoft 365 Defender portal (https://security.microsoft.com/) and sign in with your administrator credentials.
Step 2: Go to the Restricted users page
Once you are signed in, go to the “Restricted users” page by clicking this direct link: https://security.microsoft.com/restrictedusers
Step 3: Find the blocked user
On the "Restricted users" page, you will see a list of blocked users. Locate the user that you want to unblock by scrolling through the list or by using the search box.
Step 4: View details about the user
Click on the user's name to view more details about their block. The "User details" page will show you the reason for the block and the specific policies that caused it.
Step 5: Unblock the user
To unblock the user, click on the "Unblock user" button on the "User details" page. A confirmation message will appear asking you to confirm your action. Click on "Yes" to proceed with unblocking the user.
Step 6: Verify the user is unblocked
After you confirm, the user will be removed from the restricted list and will be able to access the services they were previously blocked from. You can verify this by checking the user's account and ensuring that they can access the service.