Email object customization

Advanced modification can be done on the email, using a TYPO3 signal:

my_extension/ext_localconf.php

$dispatcher = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(
    \TYPO3\CMS\Extbase\SignalSlot\Dispatcher::class
);

$dispatcher->connect(
    \CuyZ\Notiz\Domain\Channel\Email\TYPO3\EmailChannel::class,
    \CuyZ\Notiz\Domain\Channel\Email\TYPO3\EmailChannel::EMAIL_SIGNAL,
    \Vendor\MyExtension\Service\Mail\MailTransformer::class,
    'transform'
);

The object can then be modified as needed:

my_extension/Classes/Service/Mail/MailTransformer.php

namespace Vendor\MyExtension\Service\Mail;

use CuyZ\Notiz\Core\Channel\Payload;
use TYPO3\CMS\Core\Mail\MailMessage;
use TYPO3\CMS\Core\SingletonInterface;
use TYPO3\CMS\Core\Utility\GeneralUtility;

class MailTransformer implements SingletonInterface
{
    /**
     * @param MailMessage $mailMessage
     * @param Payload $payload
     */
    public function transform(MailMessage $mailMessage, Payload $payload)
    {
        $applicationContext = GeneralUtility::getApplicationContext();

        // We don't change anything in production.
        if ($applicationContext->isProduction()) {
            return;
        }

        // Add a prefix to the mail subject, containing the application context.
        $subject = "[$applicationContext][NotiZ] " . $mailMessage->getSubject();
        $mailMessage->setSubject($subject);

        // When not in production, we want the mail to be sent only to us.
        $mailMessage->setTo('webmaster@acme.com');
        $mailMessage->setCc([]);
        $mailMessage->setBcc([]);
    }
}