NOTE: After October 2025, Microsoft 365 subscriptions associated with a work or school account will no longer be able to use legacy Outlook for Mac with their subscription. Please note that the import/export function is currently not available in new Outlook for Mac.
You will need to use Legacy Outlook in order to use the Import function. Click on the Outlook menu to see if there is a checkmark beside Legacy Outlook. If not, select it. Outlook will relaunch and you will be able to continue.
Outlook for Mac can import data from an older version of Outlook, an OLM file exported from Outlook for Mac, or a PST exported from Outlook for Windows.