Is the e-mail setup through .Mac or some other provider? If it has to sync with something like yahoo, where you gave your e-mail address and password to save and automatically sync everytime you launch the app, just uncheck the option to save password. Just an idea though. Good luck.
Okay, I'd say you're old enough. I'd suggest deleting the account password in your Mail Preferences and then making sure it's not saved in your keychain when prompted but that won't prevent them from just canceling out and reading whatever messages you've already retrieved. Hmm...
Sue them? Invasion of privacy? Unless youre using something of theres to obtain the email, or whaetever. We'll let the legal people on the forums answer that.