A while back (I’m embarrassed to say how many months I’ve lived with this issue) my compose mail font became victim of the Honey I Enlarged the Font syndrome. I think I was overly passive regarding this issue because as I get older my eyesight gets worse and worse and having the font so large made me feel studly. Today I finally figured out what was going on.
I could see the front was set to 11 point but it looked more like it was at 22 points. My first clue came when I added an image to the email. It too was very large. One way to fix this issue is under the Format Text ribbon bar. Start a new message and move to the message area. Click on the Zoom icon (pointed at by the green arrow in the image You will see the dialog shown at the left. If none of the radio buttons are selected, look at the Percent field. Getting Outlook back to normal was as easy as clicking the 100% radio button. You can also adjust this setting without bringing up the dialog. Hold down the control key as you move your mouse wheel and the zoom value will change. That might be how I accidentally changed it in the first place although I think Outlook sometimes just has a mind if its own.