1. Logon to your Office 365 Security and Compliance portal.
    
2. Click on the Threat Management [1] dropdown, then Policy [2] and finally click the Anti-Phishing [3] link under Policies (as below).
   
   
   
   
3. Click on the Office 365 AntiPhish Default (Default) Rule
   
   
   
   
4. On the following screen, click on Edit Protection Settings as below:
   
   
   
   
5. Click on Manage 0 trusted sender(s) and domain(s)
   
     
   
   Note: There may be previously added senders or domains for your organisation, which would mean that the above link would not show a zero (0) value.
   
    Here you can add trusted / known email addresses and domains. 
   This will allow you to override the anti-phishing policy for added domains only.
   
    
6. On the screen that follows the Sender tab will initially be highlighted. Ignore that and click on the Domain tab as below:
   
   
   
   
7. Click the plus icon and we will then add each of the following domains listed below:

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8. When you click the plus icon, you will see the following screen. Enter the name of each domain one by one [1], and as you enter the domains they should appear as a clickable item [2] once they’re valid.
   
   Click on the domain name(s) [2] to then add as below:
   
   

   

    

9. Do not hit the Add Domains button until all the domains are added:
   
   
10. When all 21 domains have been added, click on the Add domains button.
    You will see a list of domains as below:
    
    
    
     
11. Please ensure that you’ve added all the domains correctly. Click the Done button.
    
    
12. You will then see that you’ve added the 21 domains, as below:
    
    
     
13. Finally, click Save.