I remember seeing that error message after I saved the changes. What would have helped if the error message was always there so people don’t do it. I saw individual pages on the landing page, each page in a small rectangular area on top of one another. What was scary is that when I deactivated the plugin, the change stuck. When I activated it again, it took some experimenting to undo the change. But all that doesn’t matter now.
The author of that plugin stopped his support in 2008. As it stands, I have your auto responder software that only uses the wordpress mail function which does not allow me to change the ‘from’ field. When I received test confirmation email, the link wasn’t clickable. I’m sure that if you can fix these issues your sales will sky rocket.