Sending mail to an adress specified in a node creation form with an CCK email field with Rules
As long as you have the Rules module and the Token module installed, it should be a pretty straightforward.

1) Create a rule that responds to the event "After saving new content"

2) Add an action to that rule "Send a mail to an arbitrary mail address" (from the System section)

3) Use a token for the Recipient field. As long as there is a CCK field for the email address, there will be a token provided for it. It will be listed in "Token replacement patterns."