How to whitelist addresses in Exchange Online Protection (EOP) by MisterCloudTech
How to Whitelist a Domain to Bypass Spam Filtering in Microsoft Office 365 - Rolet Support / KnowledgeBase
How to whitelist domain in Office 365 - Microsoft 365 atWork
How to allow list/whitelist/block list/blacklist incoming email address/domain in Microsoft 365 Exchange Online/Exchange Online Protection (EOP) (Or add domain/email address to safe sender list) > Blog-D without Nonsense