There's a lot of mis-information out there on the net right now about how to properly do redirection of the Outlook Web Access URL from an HTTP request to an HTTPS request. Most of this is due to how Exchange and OWA have changed over the past few versions... but some of this confusion comes from Microsoft itself, and their Technet articles! If you check out the Technet article "Simplify the Outlook Web App URL" at http://technet.microsoft.com/en-us/library/aa998359%28v=exchg.150%29.aspx, the article guides you through modifying the SSL settings, changing the HTTP redirect option, then going back through and cleaning up the mess you made in IIS due to properties inheritance on sub directories of the default website. What's worse, it doesn't even work!
As it turns out, this process is actually just a copy/paste from the Exchange 2010 process: http://social.technet.microsoft.com/wiki/contents/articles/921.simplify-the-outlook-web-app-url-in-exchange-server-2010.aspx
So... what's the right way to do this? A custom error page! It's so much simpler than all of the mess above, and the changes that are made to IIS7 to make it happen are much less intrusive, requiring no cleanup or anything.
1) First of all, log into your Exchange 2013 CU2 CAS server and open IIS7.
2) In the IIS7 Management Console, expand sites and select the Default Web Site (not the Exchange Back End site!)
3) In the center area, double click on the Error Pages icon, then on the right hand side under Actions click on "Add".
4) In the Add Custom Error Page window, under status code, enter 403.4. For the response action, select the third option "Respond with a 302 redirect" and under the Absolute URL field enter your full url, such as https://email.domain.com/owa. Don't forget the /owa on the end! Click OK to close the window.
5) Open up a command prompt and type "iisreset" to apply the changes.
That's it! Now try browsing to http://email.domain.com and validate that you are indeed redirected to https://email.domain.com/owa. So much easier! The other real benefit is that you can leave the "require SSL" box checked on the default website and OWA subdirectory using this process, and you don't have to mess with the HTTP redirect option, which has the tendency to break all of your subdirectories by applying the redirection to them as well!