If you click the Finish button without entering the From Address or Subject, the wizard will show this error. Sometimes it can get stuck on this error once it comes up and even if you correct the from Address and Subject, it will not recognize it. If this happens you will have to restart the wizard.
Make sure to enter a value for the from address and subject before clicking the Finish button. after entering the subject. You can also try using the enter key on your keyboard to force the value to stick before clicking on the finish button.