Outlook 2016, 2013 and 2010 by default displays To-Do bar on the right hand side. This contains information such as appointments and To-Do tasks. But if you are not using this feature then you can hide the To-Do bar to get more space for your Outlook Application.
To hide the To-Do bar in Outlook 2010, navigate to the View menu.
and the to layout section and click the dropdown arrow next to To-Do Bar menu and select Off from the list of available menus.