// EsmtpTransportTest.php
   
    public function testAuthExceptionContainsNoStackTrace()
    {
        $transport = new EsmtpTransport('smtp.ionos.de', 465, true);
        $transport->setUsername("test");
        $transport->setPassword("test");
        $message = new Message();
        $message->setHeaders(new Headers(
            new MailboxListHeader("From", [Address::create('[email protected]')]),
            new MailboxListHeader("To", [Address::create('[email protected]')]))
        );
        try {
            $transport->send($message);
            $this->fail("Expected TransportException");
        } catch (TransportExceptionInterface $e) {
            $this->assertStringNotContainsString("Stack trace:", $e->getMessage());
            $this->assertStringNotContainsString('Symfony\Component\Mailer\Transport\Smtp', $e->getMessage());
        }
    }