Segmentation lets administrators enable and disable OWA features including calendars, tasks, Unified Messaging integration, Public Folder and OWA Premium access. Although this is not a new feature to OWA, segmentation configuration options are now available in the Exchange Management Console (EMC), instead of having to manually calculate and edit the registry value.
The EMC allows Administrators to customize a user's OWA experience based on the Client Access Server (CAS) they connect to. Segmentation is configured on the /owa folder on the Properties page. To get to the OWA folder,
As an example, some organizations may decide to disable the "Change Password" feature which allows users to change their Active Directory user account password from within OWA, and would do so by changing the default segmentation value of "Enabled" to "Disabled". As a result, all users connecting to the /owa folder will not be able to change their password using OWA.
Advanced administrative options are available through the Exchange Management Shell which extends the Exchange Management Console's functionality by allowing OWA options to also be applied on a user level. See Microsoft's How to Manage Segmentation in Outlook Web Access information on all segmentation options.