I called Adobe on this as I was in a rush. When adding a button to submit the form by email, do not use the default "Email Submit Button". Instead use the plain "Button" in the Standard area of the Library tab. After you place this button, look in the "Object Tab" and under Control Type select the "Submit" Radio Button. A new tab labeled Submit appears. Select this and in the Submit to URL field enter: "mailto:xxxxxx [at] xxxxxxx [dot] xxx" then in the Submit As dropdown select PDF.That worked for me.
I tried this as well and it appeared to work withing Adobe Pro 9, but when users try it in Reader 7-9, there is no response after clicking the email submit button.
Phil