Are you trying to compose in rich text or plain text?
If you are using plain text the "font line" will not show where as it will if you compose in rich text.
You can change this per email by selecting rich or plain in the "Format" box in the menu bar above the email text box or by going into the email account's settings by clicking on your user name and once in the settings go to Mail then "compose messages in rich text format" and tick the box.
