How to move Email, Calendar & People Icons to Bottom Pane in Outlook
If you would like to change the icon bar from Side View to the Bottom bar view, please follow these steps.
To reset your Outlook screen options
1. Go to File 
2. Then Scroll down to Options
3. Go to Advanced to remove the check from the option to Show apps in Outlook.
3. Restart Outlook and Icon bar should be at the bottom left.