Problem: When you create a new email message, the text is very large.
Solution: the problem is that the Zoom setting is out of whack, probably set at 200%. Well, the zoom setting is located all the way on the right side on the Home tab but it is greyed out until you type at least one letter in the body of the email. Once you type a letter, adjust the Zoom setting back to 100% and close the email message. Now when you compose a new email, things should look normal.