It is not free but eM Client[0] offers a "light" version of Outlook's UI and it has the best CalDAV/CardDAV support on Windows compared to Thunderbird + Lightning or 3rd party Outlook plugins.
Currently Version 7 is still in Beta but it is stable enough to be my daily driver and it offers some important features like a message thread view, which is still missing on their current, stable 6.0 release.
Currently Version 7 is still in Beta but it is stable enough to be my daily driver and it offers some important features like a message thread view, which is still missing on their current, stable 6.0 release.
[0] http://www.emclient.com/?lang=en