The fonts cascades. Helvetica, arial, general sans serif.
If you are on a mac it is most likely Helvetica. If you dont have Helvetica it will default to Arial; if you dont have Arial it will default to general san serif. If is is a windows machine, most likely arial.
- Title of newsletter 27px
- Intro & Footer = 14px
- Article title = 20px
- Body = 14px