ATP Anti-Phishing Policy Question

Greetings,

We are just configuring the Anti-Phishing Policy (Admin Center --> Security & Compliance Center --> Threats --> Policy) and there is an option to turn on Mailbox Intelligence.  There is a disclaimer that "You can only enable mailbox intelligence for cloud-based accounts, that is, accounts whose mailbox is hosted entirely in Office 365." We have our mail entirely in the Cloud (no hybrid solution).  We are sync'd to our Active Directory, though.  Does this disclaimer mean only mailboxes that are created in the cloud with no Active Directory sync or does it include accounts that are sync'd to Active Directory?