If Microsoft could just bundle their Edge/Chromium renderer instead of their ancient WordHTML engine, or even the EdgeHTML engine of the previous Edge, they'd do the whole industry a huge favor. It's so frustrating their holding us back. Instead, they allow Google to push technologies like AMP for email for things that could probably be solved with standard HTML.

The situation is wild. In older Outlook versions they've used IE to render the received mails but used a custom engine when you were writing/editing an email. You could even use Word as an editor so you could generate the HTML using Word as your WYSIWYG IDE. I can understand why that needed some consolidation into one editor and one engine but re-using Word so they wouldn't have to create a new editor wasn't the best decision for the ecosystem.

WYSIWYG editors and rendering engines aren't things I know about so I wonder if there have been difficult engineering issues at that time or if they just went at it from a business standpoint of "people see mail like letters so they are documents for which we have word so let's use that".

//Edit: Looks like they were mainly interested in providing a great WYSIWYG experience using tools users are already familiar with: https://web.archive.org/web/20110311083708/http:/blogs.offic... great quote: "There is no widely-recognized consensus in the industry about what subset of HTML is appropriate for use in e-mail for interoperability. The “Email Standards Project” does not represent a sanctioned standard or an industry consensus in this area. Should such a consensus arise, we will of course work with other e-mail vendors to provide rich support in our products." - I guess their argument could be that there still is no "HTML standard for email" so they don't have to support anything they don't want to?

They could easily do that. But they want to use their Word component to compose replies to emails. So it needs to go through the WordHTML at some point..

And from that perspective, it's better to break the mail as it's coming in (so the sender gets blamed) rather than at the moment the user clicks reply.

Biggest joke is, they're already having a decent renderer on macOS.

You can load plain HTML as a .eml template into it and send it off... but not on Windows, you're stuck with some weird undocumented binary format there.

I will never believe or respect Microsoft's supposed "open source" renaissance until they do something about reading and writing proper HTML/CSS in Outlook-Windows. The damage from the last 15 years of WordHTML has been irreversible.