Mage2\Order\Controllers\Admin\OrderController::updateStatus PHP Method

    public function updateStatus($id, UpdateOrderStatusRequest $request)
    {
        $order = Order::findorfail($id);
        $order->update($request->all());
        $userEmail = $order->user->email;
        $orderStatusTitle = $order->order_status_title;
        Mail::to($userEmail)->send(new UpdateOrderStatusMail($orderStatusTitle));
        return redirect()->route('admin.order.index');
    }