Dave, right click on the Firefox Toolbar and select "New Bookmark." In the box which appears, enter whatever you want it called on the toolbar ans "name," then enter the complete path to the executable file (including, of course, the executable's name) for your mail program as the "location." The keyword and description boxes can be filled in or not as you wish. When you click on "OK" the 'bookmark' will appear on your toolbar and can be executed from there.