Increase Font Size in Windows 7 and Outlook 2010/2013
To increase the readability of text in Windows without lowering your resolution:
Click Start
Select Control Panel
Select Display
Choose Small, Medium or Large.
Alternatively you can set the custom font size via the option to the left.
To specifically read mail larger in Outlook you can open a message/preview window and hold CTRL on the keyboard while scrolling up on your mouse wheel.