How can I change the font settings for the Navigation Pane?
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.
To change the font settings of the Navigation Pane choose;
tab View-> button Navigation Pane-> Options…-> button Font
Changing the font of the Navigation Pane from within Outlook 2010.
For more about changing the interface formatting of Outlook see the guide;
Fonts, sizes and color settings of the Outlook interface
Outlook 2003 and Outlook 2007
Font modifications for the Navigation Pane in Outlook 2003 and Outlook 2007 can only be made via the general Appearance settings of Windows. Even then, you can only make changes to the font size (via the Menu appearance item) and the font color (via the Window appearance item). Changing the font type being used is not possible and remain Segoe UI even when you alter the font type of the Menu appearance item.
Changes you make to the Appearance settings of Windows will of course affect more than just the Navigation Pane in Outlook, so you might want to be careful with that. If the font size in general is a problem for you in Windows, then it is recommended to increase your DPI settings instead. This will increase the font sizes in pretty much all windows applications at once.
In Outlook 2003 and Outlook 2007 the Navigation Pane settings can
only be altered via general Windows Appearance settings.