Hi BigBearDuo,
To change the font size on MSN sites follow the below instructions:
a. Sign into MSN > Click customize on Navigation bar > Select text Size and Click Add and then click ok.
b. Click Text Size in Navigation Bar and then select the option which is suitable like Small, Medium, and Larger or largest.
Unfortunately you won’t be able to change the font size on Incoming Emails on MSN as it’s a Default Design. However you may change the Font size Settings on your computer by contacting Microsoft Team at 1-866-234-6020 for further assistance.
Thanks!