Email, Messaging, & Video Calls Email How to Make Yahoo! Mail the Default Email in Firefox 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 December 10, 2019 Email Yahoo! Mail Gmail Tweet Share Email Yahoo! Mail is where you go for email. Now you wish Mozilla Firefox would go there, too, to start a new message when you click on an email address, for example. Fortunately, telling Mozilla Firefox to use Yahoo! Mail as the default email program can be done without any coding and in a few clicks. Make Yahoo! Mail the Default Email Program in Mozilla Firefox To set Yahoo! Mail as your default email program in Mozilla Firefox: Open Yahoo! Mail in Mozilla Firefox.Select Options | Set Y! Mail as default webmail from the navigation bar.Now select Options | Preferences… or Firefox | Preferences… from the Mozilla Firefox menu.Go to the Applications tab.Make sure Use Yahoo! Mail is selected under Action for the mailto Content Type.Close the preferences window. In earlier versions of Mozilla Firefox, in particular, you can also turn to the Mailto 2 Webmail script for Greasemonkey to have Yahoo! Mail handle email links. Under Windows, you may also be able to make Yahoo! Mail your email program for other applications.