Until Outlook 2003 Microsoft used Internet Explorer to render HTML emails. That changed with the release of Office 2007 where they started to use Word to render HTML emails. Word is the most horrible way to render HTML. It doesn't even implement the most basic styling features like margin or padding.
These days websites need to be responsive so they will show good on all kinds of devices and screens. All these new features are great but Outlook (and now Windows 10 Mail too) is staying behind. More people are reading there mails on mobile devices these days and if Microsoft doesn't want to catch up they are going to lose more users using Outlook.
Countless initiatives have gone up since 2009 where the Office employees promised better support but 8 years after the release of Office 2007, nothing has improved.
Microsoft, It's Time to Address Outlook's Proprietary Email Format (+ Ignorant response please tell us what is wrong with it, we don't understand)
Somebody from the Channel9 team should take a camera, go to the Outlook team and ask them why they are still in this situation.