I recently found some cool fonts and I have downloaded them.
The problem is I don't now how to add new font to Thunderbird because they appear in Mozilla.
So if you could please explain to me, how to make them work.
Any help would be appreciated.
How to add new font to Thunderbird browser
Hi Susan,
I understand your intention to use your own fonts so I suggest to follow this.
You have wonderful ADD-ONS to change the font size, the add-on is Theme font & size changer is a simple browser tool that lets you change the font size and font family of Thunderbird. It is a valuable tool for  widescreen users. After installing add-on , go to status bar button click on the theme font & size changer button in your Thunderbird status-bar.Choose tools menu from the browser menu bar and click on the theme font & size changer option. It will open up Font and size changer settings panel.
In font section provides fonts currently installed on your operating system. With this option is set you will be able to find two newer font family. It does not supply you with fonts it allows you to use fonts that are already installed on your system which provides a great selection and size section in please select font size value  and the changes will be applied instantly.