createMailSection example

->append($this->createCdnSection())
                ->append($this->createApiSection())
                ->append($this->createStoreSection())
                ->append($this->createCartSection())
                ->append($this->createSalesChannelContextSection())
                ->append($this->createAdminWorkerSection())
                ->append($this->createAutoUpdateSection())
                ->append($this->createSitemapSection())
                ->append($this->createDeploymentSection())
                ->append($this->createMediaSection())
                ->append($this->createDalSection())
                ->append($this->createMailSection())
                ->append($this->createFeatureSection())
                ->append($this->createLoggerSection())
                ->append($this->createCacheSection())
                ->append($this->createHtmlSanitizerSection())
                ->append($this->createIncrementSection())
                ->append($this->createTwigSection())
                ->append($this->createDompdfSection())
                ->append($this->createStockSection())
            ->end();

        return $treeBuilder;
    }