https://www.iorad.com/player/1796090/MS-500---Ensure-that-unmanaged-mobile-devices-are-quarantined-when-the-devices-attempt-to-connect-to
You need to configure the Exchange ActiveSync Access Settings.
- Go to the Exchange admin center.
- Click on Mobile in the left navigation pane.
- On the Mobile Device Access page, click the Edit button in the Exchange ActiveSync Access Settings area.
- Select the Quarantine option under When a mobile device that isn't managed by a rule or personal exemption connects to Exchange.
- Optionally, you can configure notifications to be sent to administrators and a message to be sent to the mobile device user when a device is quarantined.
- Click Save to save the changes.
https://www.gitbit.org/course/ms-500/learn/Understanding-compliance-policies-qDRA4jjoN