Cumulative Update 11 contains the latest set of fixes and builds upon Exchange Server 2013 Cumulative Update 10.
As per Microsoft December 2015 Quarterly Exchange Update Notes,
Cumulative Update 11 for Exchange Server 2013 and UM Language Packs are now available on the Microsoft Download Center. Cumulative Update 11 contains the latest set of fixes and builds upon Exchange Server 2013 Cumulative Update 10. The release includes fixes for customer reported issues, minor product enhancements and previously released security bulletins. A complete list of customer reported issues resolved can be found in Knowledge Base Article KB3099522. Customers running any previous release of Exchange Server 2013 can move directly to Cumulative Update 11. Customers deploying Exchange Server 2013 for the first time may skip previous releases and start their deployment with Cumulative Update 11 directly.
There are two particularly important changes included in these updates:
- Cumulative Update 11 and Update Rollup 12 each contain a time zone calculation fix to resolve the issue reported in KB3048372 – Exchange Calendar Items are shifted incorrectly when some Windows DST updates are applied. Customers in impacted time zones are encouraged to deploy these updates to address the issue identified after the release of the OS time zone changes in KB3039024.
- Cumulative Update 11 also includes a change in behavior when deploying/administering Exchange Server 2013 in a co-existent manner with Exchange Server 2010 or 2016. These changes are outlined in the following blog article: Exchange Management Shell and Mailbox Anchoring.
Microsoft recommends all customers test the deployment of any update in their lab environment to determine the proper installation process for your production environment. For information on extending the schema and configuring Active Directory, please review the appropriate TechNet documentation.