If you use swiftmailer + simplenews, you may want to send html email with custom css. To achieve that,you have to customise 2 twig templates. The first template is the default template that is provided by swiftmailer: simplenews-newsletter-body.html.twig. You can use this template to build your own email body with content you like to use. For example, in the template below, an hero image is inserted using table layout.
This article is about my experience using Brotli at production scale. Despite being really expensive and a truly unfeasible method for on-the-fly compression, Brotli is actually very economical and saves cost on many fronts, especially when compared with gzip or lower compression levels of Brotli.