Is your form deployed on any server? If so, make sure that the form is not cached anywhere.
If nothing works, just rename your file.
how was the form copied from original one?
You might want to check if there's script on the form apart from the email submit button.
since the same action can be triggered by the script, it could be over riding the button's settings.
Make sure your test email is not embeded to the field.
Below is a very helpfull site, check it out, there are a lot of sample code that might help:
Open Acrobat on your machine, go to Edit / Preferences / Identity and change the info. Distribute the form with the new email address and then change the preference / identity back to the email you use for testing. Livecycle apparently hands off the form to Acrobat to finish the distribution and utilizes the preference data. This needs fixing from a Livecycle position.
I have the exact problem. I have yet to be able to solve.
STOP sending email to this account - STOP