View Someone Else'S Calendar In Outlook. The specific steps vary based on your calendar app, so i’ll show you how to check people’s availability in the various outlook apps (including the web app) as well as in the apple. Outlook 2016 and later versions have the feature to view calendars for others.

If the recipient is internal user, you could try to add it in outlook to see if you can see his free/busy time. Be using outlook web app or outlook client: