How to make Firefox 3 use Gmail or Yahoo mail when clicking email links in web pages

It's great if you use Outlook to manage all your email, but many people like to use web based email, such as GMail or Yahoo! Mail instead of downloading their email to their computer. And in this cases, users probably wished that Firefox could open there (GMai or Yahoo!) mailbox when clicking an email link on a web page. Instead, Firefox will open Microsoft Outlook (if you have it installed).
1 answer

How to configure Firefox 3 using GMail

Firefox makes it easy to select a default email application like Outlook or Thunderbird. When you click a mailto: link on a web site, that application will automatically open. But with Firefox 3 RC1 you can also choose a webmail application like Yahoo! Mail or Gmail.

Selecting Yahoo! Mail as your default email provider is simple. Just hit the Tools button, select Options, navigate to the Applications tab, and select Yahoo! Mail from the dropdown list next to "mailto." But for some reason, that's the only webmail service included by default. So thanks to Lifehacker, here are the steps to add Gmail:

1. Type about:config in the URL bar, and click the I'll be careful button to continue.
2. Type gecko.handlerservice into the filter field and find the listing that ends with allowRegisterFromDifferentHost. Click this button to change the value from false to true.
3. Copy this line of code into the URL bar:
javascript:window.navigator.registerProtocolHandler("mailto","https://mail.google.com/mail/?extsrc=mailto&url=%s","GMail")
4.
A window will pop up asking if you want to add GMail, say yes and you should be all set.

Next time you click a mailto: link on a web site, you should get a choice of services to use including Gmail. You can then set Gmail as your preferred email service.

From http://www.downloadsquad.com/2008/05/22/configure-firefox-3-to-use-gmail...