Like PornoTGB pointed out, you have to stick to this basic syntax:
mail($targetemail, $subject, $message);
Example: mail("paulazahn@cnn.com","Re:Nice interview last night", "Hey Paula, just saw your interview with the girl working for New York Confidential....");
If you want to add header info, then like on the example on
http://us2.php.net/manual/en/function.mail.php,
use: mail($targetemail, $subject, $message, $header).
In other words, mail($subject, $target_email, $header...) or any other variants like mail($header, $subject, $to_email) ... will not work.