Swiftmailer.default.plugin not fired in custom plugin

Hello, I’m developing a custom plugin and I want to make some action before an email is send.

If I set muy plugin as here https://swiftmailer.symfony.com/docs/plugins.html it works ok, but I have to change EmailBundle/Helper/MailHelper.php, something that I don’t want.

I want to register the swiftmailer plugin on my plugin config, as shown here: https://symfony.com/doc/3.4/reference/dic_tags.html#swiftmailer-default-plugin so in my plugin conf y have:

   'services' => [
            'swiftmailer.default.plugin.quota' => [
                'class' => 'MauticPlugin\CampaingExtensionBundle\EventListener\Swift_Plugins_Quota',
                'arguments' => [],
                'tags' => [

But in this case is never fired. Any help?

Have you managed to fix it? I am also trying to listen any event that will be fired before email is sent, swiftmailer.default.plugin is one of these events. I need to modify From and Reply To addresses before email is sent out.