通过Gmail发送邮件，'；bbc'；不起作用-Laravel 5.2

我正在向许多用户发送电子邮件，我想添加bbc，发送本身正在工作，但当我添加bbc时，我收到了这个错误

call_user_func_array() expects parameter 1 to be a valid callback, class 'Swift_Message' does not have a method 'bbc'

我正在张贴控制器：

use Illuminate'Http'Request;
use App'User;
use Illuminate'Support'Facades'Mail;
use App'Http'Requests;
use App'Http'Controllers'Controller;
class EmailController extends Controller
{
    public function sendEmail(){

        $users = User::where('type','student')->pluck('email');

            foreach ($users as $user) {
                Mail::send('emails.test', ['user' => $users], function ($message) use ($users, $user) {
                    $message->from('mg.kvelichkov@gmail.com', 'МГ "Константин Величков"');
                    $message->to($user);
                    $message->bbc($user);
            });
        }
        return "Your email has been sent successfully";
    }
}