It is possible to track emails sent from Outlook 365. You must use the Chrome browser and install LiveHive's Chrome extension. Once you have the extension installed you will see the LiveHive toolbar in the Outlook 365 email compose window, see the screen shot below.
There are some scenarios where adding a contact does not display the persons email address in the "To" field. In these cases the recipients name is displayed and the email is still tracked but you will see the persons name in Insights and you will not see their email address.