Sometimes the font of my newly arrived e-mail is so
small I can hardly read it. Is there an easy way to enlarge it?

Yes, but the method depends on which e-mail client or browser you use. Here are some of your choices:
If you use Outlook 2007: Press the Ctrl key as you turn
the scroll wheel on your mouse away from you. Or open the message in
its own window (by double-clicking in it) and click on Other
Actions, Zoom to pick a viewing
magnification.
If you use Outlook 2003: Same as Outlook 2007, hold down
the Ctrl key as you turn the scroll wheel. Or open the message in its
own window and click on View, Text Size to adjust the size.
Outlook Express: Same as Outlook 2003.
Gmail, Hotmail and MSN: Since they are Web–based e-mail
clients, size is dependent on your browser, and adjustments are less
predictable. You can try Ctrl++ (that’s one plus sign) to enlarge and
Ctrl+- (minus sign) to reduce magnification. Use Ctrl+0 (zero) to
reset magnification to the default value.