In Outlook 2003 and Outlook 2007, the font settings of the Navigation Pane can only be adjusted via general Windows Appearance settings.
Outlook 2010 holds a direct option to alter the font settings of the Navigation Pane.
Steps to be followed:
To change the font settings of the Navigation Pane choose;
1. Open Microsoft office outlook 2010 then click on ‘File”.
2. Now select either “Help tab” or “Options tab” as shown in above picture.
3. Then select “Advanced option” in left pane.
4. Now select “Navigation pane” option
5. Then select required options and select “Font tab” to make changes to fonts in navigation bar.