The usual reason that the server asks you to log in is that it doesn't recognize you user ID number. There is a comment in your form that says the following:
But I don't see the hidden tags you were not suppose to remove. Go back to the Email Forms service manager and get the appropriate tags. Below is an example of what they look like.
Of course, where the Xs are there will be your user number. These hidden fields are necessary to identify you to the server and determine which form processor to use.
