For me there are two ways to go about typing an email in Hotmail/Outlook.
1. Set your "standard" primary Font settings, that is what you'll see in every email.
2. "If" you wish a particular email to have a larger font, type out the email, then at the end, highlight all of the text, then go to the tool bar and you can change the font size, style or color. Your standard settings will not change, however that one email will look as you please!
How to get to your "standard primary" setting:
Click on the gear next to your name at the upper right corner
Click on Options
Scroll down to "Writing Email"
Find Formatting, font and signature
Message Font will show, there is where you can set your standard primary font setting (e.g. font style, font size, font colour)
Sure hope that helps! LOL ~ when I know I'm sending an email to a pal who is computer screen reading challenged, I love to change the font size to 14 or 16 !! It seems huge, however I know they greatly appreciate the font size!