Open Outlook
Go to File
Select Options
Click Mail
Under Compose messages, click Stationery and Fonts
Choose the font size you want for new messages, replying, and plain text messages
Click OK
To make text bigger while reading an email, use the zoom slider in the message window
To make the reading pane text larger, open the email and increase the zoom level
To change the font size in the Outlook interface, go to View
Select View Settings
Choose Other Settings
Adjust the font size for column headings and row fonts
Click OK to save changes