To print messages:

Select one or more messages to print.

Choose File > Print.
If necessary, choose Mail from the pop-up menu under Orientation.

Select one of the following Mail options. The option will apply each time you print from Mail, until you change it.
Scale message to fit: The printed message looks the way it does on the screen. To fit the paper size, Mail reduces font sizes and graphics, but does not rewrap lines.
Rewrap message to fit: The printed message looks different from what you see on the screen. Mail keeps the font sizes but rewraps lines to fit the paper size. Do not use this option for structured text that contains indented or nested lines.
Keep the same apparent font size: The printed message looks similar to what you see on the screen. Mail uses font sizes that appear to be the same size as those used on the screen, and rewraps lines as necessary. If you're unsure which option to use, try this one first.

When you are satisfied with the preview of the printed message that’s shown, click Print.