Send a test mail from the admin and log why delivery failed

Form submissions marked as not sent gave no reason: the transport
exception was swallowed. Every send now goes through MailCheck, which
logs the server's answer and a hint in German to var/log/mail.log
(server lines only, no credentials). The system screen shows the mail
route, sends a test mail to any address and lists recent attempts
(ADR 121).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/Controller/FormController.php

@@ -8,11 +8,10 @@ use App\Content\MenuRepository;
 use App\Content\PageRepository;
 use App\Content\SiteSettings;
 use App\Content\Turnstile;
+use App\Ops\MailCheck;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
-use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
-use Symfony\Component\Mailer\MailerInterface;
 use Symfony\Component\Mime\Email;
 use Symfony\Component\Routing\Attribute\Route;
 
@@ -29,7 +28,7 @@ final class FormController extends AbstractController
         private PageRepository $pages,
         private MenuRepository $menus,
         private SiteSettings $settings,
-        private MailerInterface $mailer,
+        private MailCheck $mail,
         private Turnstile $turnstile,
         private string $secret,
         private string $siteOrigin,
@@ -127,15 +126,10 @@ final class FormController extends AbstractController
         if ('' !== $replyTo && '' !== ($values[$replyTo] ?? '')) {
             $email->replyTo($values[$replyTo]);
         }
-        try {
-            $this->mailer->send($email);
 
-            return true;
-        } catch (TransportExceptionInterface) {
-            // The submission is already stored, so a broken mail setup loses no enquiry.
-            // It stays marked as undelivered and is visible in the administration.
-            return false;
-        }
+        // The submission is already stored, so a broken mail setup loses no enquiry. It stays
+        // marked as undelivered, and var/log/mail.log says why (System -> E-Mail-Versand).
+        return $this->mail->send($email, 'Formular '.$form['slug'])['ok'];
     }
 
     /**