The tiny program that allows you to select Yahoo! Mail as the default email application for your PC is included as part of Yahoo! Toolbar version 7.2 and up for Internet Explorer (not Firefox).
If you don't have Yahoo! Toolbar v.7.2 or later for Internet Explorer installed, you’ll need to download it before proceeding with these instructions.
We’re sorry there’s not an official version for the Mac—yet.
Here’s how to set your PC to open Yahoo! Mail when you click an email link on a web page.
Note: Yahoo! Toolbar v.7.2 and above for Internet Explorer (not Firefox) is the download that adds Yahoo! Mail to your PC's list of email programs to choose from. But after you've chosen Yahoo! Mail as your PC's default email application, Yahoo! Mail will open when you click an email link in any browser.