Show Fixed-width Temporarily shows the current plain text message in fixed-width text.
This extension is useful if you normally view plain-text messages with a variable-width font (which is easier to read than a fixed-width font) but wish to view one in a fixed-width font temporarily. Such emails might be text arranged in columns, such as log files, where a variable-width font misaligns the text.
A button is added to the Toolbar (right-click on Toolbar and Customize…). Clicking on it shows the current plain text message in a fixed-width font. The effect only lasts for the current message and automatically reverts back to the default setting (as set in Options) for the next message. You don't have to click on the button again to revert back to the default state.