Email, Messaging, & Video Calls Email How to Change the Font for Incoming Mail in Thunderbird Read your email in the font you prefer by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on February 14, 2020 fill/Pixabay Email Yahoo! Mail Gmail Tweet Share Email You can set Thunderbird to use the font face and size you prefer when reading incoming mail—and pick your favorite color, too. Here's how. The procedures here were performed in Thunderbird 68.4 running on macOS version 10.15 (Catalina), but they are similar in other versions and platforms. Using your preferred fonts instead of Thunderbird's defaults might make some emails look different than what their senders intended. Select Thunderbird > Preferences (Tools > Options on a Windows computer) from the Thunderbird menu bar. Click Display. Select the default font and size you prefer. To change colors, select Colors. When you're happy with your choices, hit OK to return to the Formatting menu. Select Advanced. Make the choices as desired and hit OK. Uncheck the box next to Allow messages to use other fonts so that your choices will override those of senders.