Yahoo will apply a preferred font size and type-style to all of your emails. You can also rely on its built-in font formatting tools to accentuate or downplay portions of individual mail messages. But to improve Yahoo email readability, turn to your Web browser, keyboard or touch screen instead.
Reconfigure Your Default Font
Click your Yahoo email's gear icon. Next, choose "Settings," followed by "Writing email." The Default Rich Text Font section displays the font attributes that are automatically applied to your emails. Select a more acceptable font style or size from the drop-down menus, using the generated sample as your guide. You have seven font faces to choose from and four size options -- small, medium, large and extra large.
Reformat an Individual Email
You can change the font size and style of certain parts of a Yahoo email message for emphasis or aesthetics. Begin by selecting the text you wish to reformat, then click the "Tt" icon and choose a desired font and size from the pop-up menu. You can't make these changes if you're writing in plain-text mode. Click ">>" to switch to rich-text mode before attempting to reformat your text.
Resize for Viewing Purposes Only
To improve the readability of your Yahoo emails, use your Web browser's zoom controls to make them appear larger or smaller on your screen. Alternatively, on a PC, press "CTRL" while you roll the mouse's scroll wheel or press "+" or "-." On a mobile device, spread or pinch your fingers on the touch screen.