I always have to change the font when I send messages from my computer. I tried dragging the Smaller/Bigger text button on to the toolbar and it doesn't allow me to use it.. anyone else having this problem? 😕
The buttons are grayed out on mine too, but you can go into Mail's preferences and change the font size under the "Fonts & Color" tab and it will stay that size, use the "Message font" box to change just the Compose mail font.