Outlook 2007 Email font

I am looking to change the default Calibri font to Times Roman for all emails, all clients in the domain. I was hoping this was a GPO setting, but no luck.

Furthermore, Outlook 2007 apparently does not let you configure default styles, or add custom styles, so this option is also useless.

What controls the +Body style in Outlook 2007. If this can be configured, I can find a way to push it to all clients.