// To send HTML mail, the Content-type header must be set

$headers = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";

// Additional headers
$headers .= 'To: ABC , def ' . "\r\n";
$headers .= 'From: Me ' . "\r\n";
$headers .= 'Cc: pqr@pqr.com' . "\r\n";
$headers .= 'Bcc: pqr@pqr.com' . "\r\n";

// Mail it
mail($to, $subject, $message, $headers);