Whitelisting an email or a domain
1. Open the URL - https://security.microsoft.com/
2. From the left main menu click Email & Collaboration
3. Click the Policies & Rules and click into the Threat policies
4. On the Threat policies page choose to which Policy you would like to add the email/domain you like to whitelist.
5. In this tutorial I did choose the Anti-spam policies.
6. Choose the Kings Spam Filter and Anti-spam inbound policy (Default)
7. Scroll to the bottom of the page and click Edit allowed and blocked senders and domains link.
8. Under the Allowed - Senders add the email you want to whitelist and Save.