When Microsoft released the Windows 8 last year, it came with an email app called the Mail App from Microsoft and you could configure multiple accounts like Yahoo mail, Hotmail, Outlook.com, Gmail, AOL and others. Although the mail app had most of the basic features, it was lacking in a good interface along with some feature available in the Outlook.com
But now with the release of Windows 8.1 (General availability on October 17th), Microsoft has redesigned the app with new features and a better UI. The interface now has blue colors (instead of the grey in old version) and has been carried over from Outlook.com web interface. The folders now have new icons and the newsletters and social updates folder.
There is not much change in the new email (compose) window, but overall there has been a vast improvement in the features and interface.
Here is a video review of the new features and interface of Windows 8.1 Mail app.