config.php: How to override the Mailer settings in Shopware 5.2.7?

Hello,

I'm using Shopware 5.2.7 with Mailer Settings for sendgrid.com, which works fine.

For local development I'd like to override the mail settings with config.php with settings as seen here for instance. But if I add a "mail" block with the following settings, it simply gets ignored by Shopware.

// Make sure no email is sent to the outside world
'mail' => [
    'type' => 'file',
    'path' => $this->DocPath().'mails'
],

How can I override the Mailer settings in Shopware 5.2.7?

Thanks a bunch!

Edit: Changed config_local.php to config.php for easier understanding.