Some people look for the Send button when they need to be looking for the Write button. The Send button appears in the screen where you write messages. If the Write screen doesn't have a toolbar, which is where the Send button should be found, try F10 or the alt key to make the menu appear, then select View then Toolbars and select the Mail Toolbar. I'd suggest that you also need the Menu Bar selected. Right-click on the title bar at the top may also present an option to select Toolbars. Which part of it do you want to change font size in? Messages? And is that in messages you write, messages that are sent to you, or both? Or is it the menus and lists that are too small?