How do I restore the font theme (not size) for some (not all) incoming emails?

This question relates to the font theme or type and not its size.  When I recently attempted to change the default font theme or type, of my outgoing and incoming emails on my (Windows 7) laptop Windows Live Mail, I somehow managed to click on to something which has since converted some but not all incoming only emails from default Calibri to something resembling Lucida Calligraphy which is not at all easy on my eyes.  Can someone please help me restore the default font theme back to factory settings or something similar?  I simply cannot retrace my steps to do it unaided.  Thank you.