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().
Parameter
array $headerEx - Additional headers, the
format of the argument is $array["header-name"] =
"header-value"
Return value
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().
