In some occasions when you click on an email link while browsing some webpages, you will be prompted with email clients such as Microsoft Window Mail for Vista or Microsoft Outlook Express for XP. If your email client has yet to be configured, you need to set up and configure it before you can send out emails. It is quite troublesome and inconvenient if you haven’t done so. Anyway, if you are Gmail and Firefox users, the good news is the new Firefox 3 allows users to configure and set Gmail as a default email client. This latest Firefox 3 comes with support YahooMail as default email client. For Gmail users, some setting needs to be done to edit the “mailto” application handler.

  • At the Firefox 3 address bar, you need to type in “about:config” and you will be prompted with a warning page. Just click on “I’ll be careful, I promise!” button to proceed.
  • Type in “gecko.handlerService” into Filter box until you get gecko.handlerService.allowRegisterFromDifferentHost Preference name. Make sure the value is “True”. Change it if it is not.
  • Also check for network.protocol-handler.external.mailto Preference name. Make sure the value is “True”.
  • Copy the following code to the address bar and press ENTER.


  • Copy the following link and press ENTER if you are a Google Apps user:


    Change to your own domain name.

  • Firefox 3 will thence prompt you a question whether you want to add application. Click on the “Add Application” button.
  • Now you click any mailto: link and you will prompt with a small window “Launch Application”. Firefox 3 requests your confirmation on which applications to be used. Check the “Gmail” box and also check the box showing “Remember my choice for mailto links”. Click OK
  • The process is done. Anyway, for safety reason, it is advisable to go back to “about:config” and set gecko.handlerService.allowRegisterFromDifferentHost value back to false.

If you have decided to remove Gmail as your default mail client, you need to 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.

For user using Yahoo! Mail, here’s how to set Yahoo! Mail as default email client in Firefox.