Microsoft has released Cumulative Update 6 for Exchange Server 2013. From the Microsoft Exchange Team blog:

CU6 represents the continuation of our Exchange 2013 servicing and builds upon Exchange 2013 CU5. The release includes fixes for customer reported issues, minor product enhancements and previously released security bulletins. A complete list of customer reported issues resolved in Exchange 2013 CU6 can be found in KB 2961810. Customers running any previous release of Exchange 2013 can move directly to CU6 today. Customers deploying Exchange 2013 for the first time may skip previous releases and start their deployment with CU6 as well.

CU6 delivers several important updates for public folder scale (now supports up to 100k folders instead of 10k) and behavior. These changes are detailed here. Also includes is the fix for the Subtask CheckPrereqs execution failed bug in the Hybrid Connectivity Wizard. Customers who have already deployed the interim update for this bug do not need to uninstall the IU before applying CU6. A list of the issues fixed in Exchange Server 2013 CU6 is available here. Updates of interest include:

Cumulative Update 6 is available for download here. For deployment steps refer to installing cumulative updates for Exchange Server 2013.


  • Exchange Server 2013-only environments – no reported issues, non-critical update, test thoroughly or wait and see.
  • Exchange Server 2013/Office 365 Hybrid – important update required, refer to this article.
  • Exchange Server 2013/2010 co-existence – no reported issues, non-critical update, test thoroughly or wait and see.
  • Exchange Server 2013/2007 co-existence, important update required.

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About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Chas

    Hi Paul,

    I’ve noticed that when installing CU6 for Exchange 2013, the following happens:
    – a new internet receive connector exists with remoteip range set to, local IP specified for the server, custom FQDN, anonymous ticked.
    – installation of CU6 spits out an error saying you cannot have two receive connectors with same remoteip ranges or similar ports (to overcome this error I had to change the remoteip range of new internet connector to a random number and change the port it was listening on to port 26. This is described in the following article:

    Is this a bug? Should I be able to create a new internet receive connector without running into IP addressing issues? The original internet receive connector out of the box was left intact, but anonymous was removed, or should I not be doing things this way?

    Thanks heaps.

      1. Lizsara

        So nice of you to point out the mistake 🙂

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