Outlook Mail & Calendar app has been updated for Windows 10 Mobile for some devices with major improvements. The latest version of app is build 17.6769.40522.
Now, with this update emails are now rendering very well than ever before. The seems to be not available to every devices. However, luckily we got the update on our Lumia 640 which is running on Windows 10 Mobile Redstone Build 14291 (using the hack).