- For stand-alone Exchange Online Protection
For safe sender and blocked sender lists to be respected, directory synchronization must be enabled. By default, safe domains are not synced through directory synchronization. You can modify the configuration to have safe domains synced to Exchange Online and recognized. For more info about how to do this, see Configure content filtering to use safe domain data.
- For Exchange Online
By default, safe domains are not recognized in Exchange Online. This is by design. As a workaround, admins can create a domain-based safe sender by using Exchange transport rules. For more info about how to do this, see Create a domain or user-based safe sender or blocked sender list using transport rules.