Outlook is unable to access contacts stored in the macOS Contacts app, including iCloud contacts. You must copy these contacts to your W-Exchange account to access them from Outlook for macOS.
- Open the macOS Contacts application.
- Click View in the menu bar and select Show Groups.
- Click All iCloud from the groups list and select the contacts you would like to copy
- Drag the selected contacts to your Contacts folder on W-Exchange.