|Vista Mail? I wonder if you mean "Windows Mail" or "Windows Live Mail". |
The size of received mail text is set by the sender. However, see this for Windows Live Mail:
Also it can sometimes be temporarily enlarged for viewing by holding the Ctrl key and turning the mouse scroll wheel.
There are ways to increase the system text size but I assume it is only email that you want to change.
Always pop back and let us know the outcome - thanks