page won't redirect and won't send mail

<?php
require __DIR__ . '/vendor/autoload.php';
date_default_timezone_set('Europe/Paris'); 

/*
$log = new Monolog\Logger('name');
$log->pushHandler(new StreamHandler('app.txt', Logger::WARNING));
$log->addWarning('oh no');
*/

$app = new \Slim\Slim(array(
    'view' => new \Slim\Views\Twig()
));

$view = $app->view();
$view->parserOptions = array(
    'debug' => true,

);
$view->parserExtensions = array(
    new \Slim\Views\TwigExtension(),
);

$app->get('/', function() use($app){
 $app->render('about.twig');
})->name('home');

$app->get('/contact', function() use($app){
  $app->render('contact.twig');
})->name('contact');

$app->post('/contact', function() use($app)
{
  $name = $app->request->post('name');
  $email = $app->request->post('email');
  $msg = $app->request->post('msg');

  if(!empty($name) && !empty($email) && !empty($msg)) {
    $cleanName = filter_var($name,FILTER_SANITIZE_STRING);
    $cleanEmail = filter_var($email,FILTER_SANITIZE_EMAIL);
    $cleanMsg = filter_var($msg,FILTER_SANITIZE_STRING);

  } else {
    $app->redirect('/contact');
  }

  $transport = Swift_SendmailTransport::newInstance('/usr/sbin/sendmail -bs');
  $mailer = \Swift_Mailer::newInstance($transport);

  $message = \Swift_Message::newInstance();
  $message->setSubject('Email from our website');
  $message->setFrom(array($cleanEmail => $cleanName  ));
  $message->setTo(array('treehouse@localhost'));
  $message->setBody($cleanMsg);

  $result = $mailer->send($message);

  if($result > 0) {
    $app->redirect('/');
  } else {
    $app->redirect('/contact');
  }

});


$app->run();

?>