Returns an array with the headers needed to prepend to the email (MIME-Version and Content-Type). Please note that the function get() has to be called before calling headers().
array $headerEx - Additional headers, the format of the argument is $array["header-name"] = "header-value"
boolean $overwrite - Overwrite already existing headers. When FALSE, the values already set are kept.
array - an associative array with the mime headers and the additional headers. The return value can directly passed to the second parameter of Mail::send().
This function can not be called statically.
Mail_Mime::headers() has to be called after Mail_Mime::get().