Does email clients such as Microsoft Window Mail or Microsoft Outlook Express prompt up everytime you click on an email link?. If you are a Firefox 3 user and use Gmail frequently, then you can configure and set Gmail as a default email client. The latest Firefox 3 comes with support of 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, type about:config and you will be prompted with a warning page as shown below. Just click on I’ll be careful, I promise!
Type in gecko.handlerService into the Filter box until you get gecko.handlerService.allowRegisterFromDifferentHost Preference name.

Make sure the value is True. Change it if it’s already not, by double clicking on it.

Also check for network.protocol-handler.external.mailto Preference name, by typing it in Filter bar.

Make sure the value is True.
Now copy the following code in the address bar and press ENTER.
javascript:window.navigator.registerProtocolHandler("mailto","https://mail.google.com/mail/?extort=mailto&url=%s","GMail")
Copy the following link and press ENTER only if you are a Google Apps user
javascript:window.navigator.registerProtocolHandler("mailto","https://mail.google.com/a/example.com/mail/?extsrc=mailto&url=%s","GMail")
Firefox 3 will thence prompt you a question whether you want to add application. Click on the “Add Application” button.

Now to set Gmail as default client, click any email link and on the window that opens, select Gmail from the list and check Remember my choice and press OK.
IF You Want To Revert Back To Old Email Client
If you ever want to revert back to your default windows mail client, follow these simple steps:
Navigate To Tools > Options > Applications in Firefox 3.

Change the selection of now default Gmail client in mailto option to windows default Live Mail Client or any other of your choice.

And you are done


