Expected response code 250 but got code "550", with message "550 5.7.1 Client does not have permissions to send as this sender

Mail::send('contact',  $user , function($message) use ($user)
    {
        $message->from($user['email'], $user['firstname']);

        $message->to('support@example.com', 'contact us' )->subject('Contact us');
    });