The default email client depends on the email program, if any, you have installed on your computer. If a user name and/or a password is required to access the email client you can enter it on this page. Alternatively you can select the Display E-mail client login dialog option to let the email client prompt you with a login dialog if required.
To test the default email client click on the Test button. This will generate and send a test message to your current email address (this is the address that you supplied when registering CDGFix 3 Super - see the License Key dialog for details).