MAILER_URL=smtp://w00d8ef1.kasserver.com:25?encryption=ssl&auth_mode=login&username=myusername&password=mypassword

swiftmailer:
    url: '%env(MAILER_URL)%'
    spool: { type: 'memory' }

$message = (new Swift_Message('Test'))
    ->setFrom('info@lama.resper.de')
    ->setTo($user->getEmail())
    ->setBody(
        $this->renderView(
            'pdf/usercard.html.twig',
            ['user' => $user]
        ),
        'text/html'
    )
;
$mailer->send($message);