Normally using firefox 2, when I click on the mailto: link, it will prompt out the Microsoft Window Mail(vista) or Microsoft Outlook Express (XP). Today I’ve get a good news for you who use Gmail. The latest Firefox 3 RC1 come with support YahooMail while left GMail user cannot use the function. Here is the configuration of GMail user to set the mailto: application handler.

1. Type about:config into Firefox 3 address bar. Firefox will come out a warning page and just click “I’ll be careful, I promise!” button to proceed.
2. Type gecko.handlerService into Filter box until you get gecko.handlerService.allowRegisterFromDifferentHost Preference name. Change the value from false(default) to true.

Warning: This configuration change disables a security feature that ships with Firefox 3, which prevents your browser from registering link protocol handlers from a domain other than the one it’s registering. Read more about what gecko.handlerService.allowRegisterFromDifferent Host does, and only proceed if you understand the risk. Don’t worry, you can set the value right back to false when we’re done.
3. Check for another preference name, network.protocol-handler.external.mailto value should be change to true.

4. Copy the following code to the address bar and press enter:

javascript:window.navigator.registerProtocolHandler(”mailto”,”https://mail.google.com/mail/?extsrc=mailto&url=%s”,”GMail”)

If you are Google Aps user, use the following link:

javascript:window.navigator.registerProtocolHandler(”mailto”,”https://mail.google.com/a/example.com/mail/?extsrc=mailto&url=%s”,”GMail”)

5. After you press enter, firefox will prompt you to ask you Add Application.

6. Now you click any mailto: link and you will prompt out a screen like below:

Click on the GMail and check the box for Remember my choice for mailto links if you wan to set it permanently using GMail.

To be safety, head back to about:config and set gecko.handlerService.allowRegisterFromDifferentHost value back to false.

To remove the GMail application, just go to Firefox’s Tool menu and select Preference then go to Application tab. Find mailto and select Application Detail from the Drop-down menu. Remove GMail by select GMail and click remove. You’re done.