Hello there We have read the message We try to help you in general usage covers almost everything https://support.mozilla.org/en-US/kb/thunderbird-accessibility-features The settings are also incorporated in your Thunderbird menu bar.. In the Thunderbird bar go to tools and options and then to advanced. Click on the configuration editor option at the bottom right. There will be a checkbox for accept risk. accept this. type pixelsp in the input field. layout.css.devPixelsPerPx will appear in front of you and here you can enter a value, try 1.5 . Do you have a preference for setting Window text? You can adjust this via: Settings, Accessibility, Screen and Make text larger. You can use the slider to determine the desired size of the font. You can also use a good add_onn for these . There is another way to change the size of the letters only in the inbox. Greetings firefox volunteer