To enable SSL redirection to the OWA virtual directory, follow these steps:
Start IIS 7 Manager.
Expand the server, expand Sites and select the Default Web Site.
Double-click HTTP Redirect.
Select the Redirect requests to this destinationcheck box, and then enter /owa.
Select the Only redirect requests to content in this directory (not subdirectories)check box.
Select Found (302) from the Statuscode drop-down list.
Click Apply to save the settings.
Note The changes that you made to the Default Web Site will propagate down to the virtual directories for that site.
Expand the Default Web Site.
Select the aspnet_client virtual directory.
Double-click HTTPRedirect.
Clear the check box for Redirect requests to this destination.
Click Apply to save the settings.
Repeat steps 9-12 for the following virtual directories:
Autodiscover
Ecp
EWS
Microsoft-Server-ActiveSync
OAB
Owa
PowerShell
PowerShell-Proxy
Rpc
##reference site
https://support.microsoft.com/en-us/kb/975341
