How to clear css style for email message?

Hi
How to clear css/html style for email message ?
The default font size for email is 12-px , I cannot change the size by Editor on Email&Message tab .
Please help me , thanks.

Hi

Sorry. Could you please explain where you can see that font-size ?

Tuan

HI
I watch and compare the font-size with the default Joomla email message and membership pro email message.
The default email message font-size is 9 px, the membership pro is 12 px.
I cannot change some html tag by Editor on Email&Message , for like I cannot change <font-size> , <br>..
help ~