HTML Email Development Is Like Web Development from 2003 (And That Is Not Changing)

If you have ever built a web page with modern CSS -- flexbox, grid, custom properties, media queries -- and then tried to build an HTML email, the experience is jarring. Email clients render HTML using engines that range from reasonably modern (Apple Mail, iOS Mail) to ancient (Outlook using the Word rendering engine). The result is that HTML email development requires techniques that web development abandoned two decades ago. Why email HTML is stuck in the past The rendering engine landscape: Apple Mail/iOS Mail : WebKit-based, supports most modern CSS Gmail : Strips <style> blocks in many contexts, requires inline styles Outlook 2007-2019 : Uses Microsoft Word's HTML rendering engine, which does not support float, flexbox, grid, or even basic CSS positioning Yahoo Mail : Inconsistent CSS support, strips some properties Outlook.com : Different engine from desktop Outlook, better CSS support but still limited Because Outlook (desktop) uses Word's renderer, you cannot use: display: flex