When you are more used to with some application software and if you use it daily on a high volume, it's sometime good to learn the keyboard shortcuts of the features that you perform regularly. Outlook exposes a lot of such shortcut keys for you to perform better.
It's not always possible to learn all of them, but good to have the list to learn/view time to time. Here I am listing all the shortcuts of Outlook 2010 - 2016, for your reference.