To make Firefox 3 use Hotmail for mailto links, do the following.
- Type about:config in the location bar and hit enter. A warning will come up. Click “I’ll be careful, I promise!” The about:config window will appear.
- At the top of the window, you’ll see a filter field. Type “gecko” in this field. The first entry you should see is “gecko.handlerService.allowRegisterFromDifferentHost”; double-click this entry to change the value to true (a true value is bold).
- Click Tools–>Options–>Applications. Find “mailto”. In the drop-down, select “Use Hotmail”. Exit the Options window.
- Type about.config in the location bar – once again click “I’ll be careful, I promise!” – In the filter, type gecko. Now, double-click on the “gecko.handlerService.allowRegisterFromDifferentHost” entry to return the value to false.