How to Whitelist an Email Address in Office 365

1. Open Microsoft 365 Defender
2. Click on Policies and Rules and choose Threat Policies
3. Open the Anti-Spam policies
4. Scroll all the way down in the fly-out and click on Edit allowed and blocked senders and domains
5. Under Allowed open Manage sender(s)
6. Click Add senders to add a new sender to the list
7. Click Done and save to apply the settings

Emails from the sender are now excluded from the spam filter and should arrive in the inbox of the users.