Microsoft has expanded Outlook over the years to absorb MSN and Hotmail, and also its Mail and Calendar applications.Jakub Porzycki/NurPhoto via Getty ImagesMicrosoft Outlook is an email platform with productivity features like calendar and file-sharing.Microsoft discontinued its old email platforms, MSN and Hotmail, and folded them into Outlook.Outlook is free for personal accounts, but paid subscriptions offer greater storage and security.In case you hadn't noticed, Microsoft has a released a lot of software over the past five decades.