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>

tests/MailCheckTest.php

@@ -0,0 +1,117 @@
+<?php
+
+namespace App\Tests;
+
+use App\Ops\MailCheck;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Mailer\Envelope;
+use Symfony\Component\Mailer\Exception\TransportException;
+use Symfony\Component\Mailer\SentMessage;
+use Symfony\Component\Mailer\Transport\TransportInterface;
+use Symfony\Component\Mime\Email;
+use Symfony\Component\Mime\RawMessage;
+
+/**
+ * Versand mit Protokoll (ADR 121): huefner-gartenbau.de zeigte zweimal „Nicht versendet“, und
+ * nirgends stand, warum.
+ */
+final class MailCheckTest extends TestCase
+{
+    private string $log;
+
+    protected function setUp(): void
+    {
+        $this->log = sys_get_temp_dir().'/kant-mail-'.bin2hex(random_bytes(4)).'/mail.log';
+    }
+
+    protected function tearDown(): void
+    {
+        @unlink($this->log);
+        @rmdir(dirname($this->log));
+    }
+
+    public function testAFailedSendSaysWhyAndKeepsTheCredentialsOutOfTheLog(): void
+    {
+        $fehler = new TransportException('Failed to authenticate on SMTP server with username "formular@kant-it.de" using the following authenticators: "LOGIN". Authenticator "LOGIN" returned "Expected response code "235" but got code "535", with message "535 Authentication credentials invalid".');
+        $fehler->appendDebug("< 220 smtp.ionos.de ESMTP\n> EHLO cms.test\n< 250 AUTH LOGIN PLAIN\n> AUTH LOGIN\n< 334 VXNlcm5hbWU6\n> Zm9ybXVsYXJAa2FudC1pdC5kZQ==\n< 334 UGFzc3dvcmQ6\n> R2VoZWltMTIz\n< 535 Authentication credentials invalid\n");
+        $mail = new MailCheck($this->transport($fehler), 'smtp://formular%40kant-it.de:Geheim123@smtp.ionos.de:587', $this->log);
+
+        $ergebnis = $mail->send($this->email(), 'Formular anfrage');
+
+        self::assertFalse($ergebnis['ok']);
+        self::assertStringContainsString('535', $ergebnis['meldung']);
+        self::assertStringContainsString('lehnt die Anmeldung ab', $ergebnis['hinweis']);
+        self::assertStringContainsString('< 535 Authentication credentials invalid', $ergebnis['dialog']);
+        // Was der Client schickt, bleibt draußen: bei AUTH LOGIN sind das Benutzer und Passwort.
+        self::assertStringNotContainsString('R2VoZWltMTIz', $ergebnis['dialog']);
+        self::assertStringNotContainsString('> ', $ergebnis['dialog']);
+
+        $protokoll = (string) file_get_contents($this->log);
+        self::assertStringNotContainsString('R2VoZWltMTIz', $protokoll);
+        self::assertStringNotContainsString('Geheim123', $protokoll);
+        $eintrag = $mail->recent()[0];
+        self::assertFalse($eintrag['ok']);
+        self::assertSame('Formular anfrage', $eintrag['anlass']);
+        self::assertSame('info@huefner-gartenbau.de', $eintrag['an']);
+        self::assertSame('formular@kant-it.de', $eintrag['von']);
+    }
+
+    public function testTheRouteNamesServerAndUserButNeverThePassword(): void
+    {
+        $route = (new MailCheck($this->transport(null), 'smtp://formular%40kant-it.de:Geheim123@smtp.ionos.de:587', $this->log))->route();
+        self::assertSame(['art' => 'SMTP', 'ziel' => 'smtp.ionos.de:587', 'benutzer' => 'formular@kant-it.de', 'gueltig' => true], $route);
+
+        self::assertFalse((new MailCheck($this->transport(null), 'kein dsn', $this->log))->route()['gueltig']);
+        self::assertSame('sendmail des Servers', (new MailCheck($this->transport(null), 'sendmail://default', $this->log))->route()['art']);
+    }
+
+    public function testAnAcceptedMailIsLoggedWithWhatToCheckIfNothingArrives(): void
+    {
+        $mail = new MailCheck($this->transport(null), 'smtp://u:p@smtp.ionos.de:587', $this->log);
+        $ergebnis = $mail->send($this->email(), 'Testmail');
+
+        self::assertTrue($ergebnis['ok']);
+        self::assertStringContainsString('intern zu', $ergebnis['hinweis'], 'Microsoft 365 beim Kunden, Domain auch beim Hoster: der häufigste Grund für „angenommen, nie angekommen“.');
+        self::assertTrue($mail->recent()[0]['ok']);
+    }
+
+    public function testTheHintsCoverTheUsualCauses(): void
+    {
+        self::assertStringContainsString('nicht erreichbar', MailCheck::hinweis('Connection could not be established with host "ssl://smtp.ionos.de:465": stream_socket_client(): Unable to connect', 'smtps'));
+        self::assertStringContainsString('SMTP', MailCheck::hinweis('Expected response code "220" but got an empty response.', 'sendmail'));
+        self::assertStringContainsString('Absender', MailCheck::hinweis('Expected response code "250" but got code "550", with message "550 Sender address rejected".', 'smtp'));
+        self::assertStringContainsString('ungültig', MailCheck::hinweis('The "foo" scheme is not supported; supported schemes for mailer "smtp" are: "smtp", "smtps".', 'foo'));
+        self::assertStringContainsString('null://null', MailCheck::hinweisNachErfolg('null'));
+    }
+
+    private function email(): Email
+    {
+        return (new Email())->from('formular@kant-it.de')->to('info@huefner-gartenbau.de')->subject('Anfrage')->text('Test');
+    }
+
+    /** Ein Transport, der nichts verschickt: wirft $fehler oder meldet „angenommen“. */
+    private function transport(?TransportException $fehler): TransportInterface
+    {
+        return new class($fehler) implements TransportInterface {
+            public function __construct(private ?TransportException $fehler)
+            {
+            }
+
+            public function send(RawMessage $message, ?Envelope $envelope = null): ?SentMessage
+            {
+                if (null !== $this->fehler) {
+                    throw $this->fehler;
+                }
+                $gesendet = new SentMessage($message, $envelope ?? Envelope::create($message));
+                $gesendet->appendDebug("< 250 2.0.0 Ok: queued\n");
+
+                return $gesendet;
+            }
+
+            public function __toString(): string
+            {
+                return 'test://';
+            }
+        };
+    }
+}