RSForm! Pro - Custom scripting. RSForm!Pro - Could not instantiate mail function error. Every time i try to submit a form a i am getting a Could not instantiate mail function. error. As you might have guessed, this can only occur if you emails will be generated. The error itself can be generated by a bunch of reasons - from improper RSForm! Pro emailing configuration to server side mailer failure. RSForm!Pro - Adding a gif to the submit button. RSForm!Pro - How do I add an image to a submit button ?