Microsoft has announced an important update is available to resolve an issue with the Hybrid Connectivity Wizard in Exchange Server 2013.

For Exchange 2013 organizations creating new or managing an existing hybrid configuration with the HCW, the following HCW error message indicates you are experiencing the issue this update addresses:

Subtask CheckPrereqs execution failed: Check Tenant Prerequisites Deserialization fails due to one SerializationException: Microsoft.Exchange.Compliance.Serialization.Formatters.BlockedTypeException: The type to be (de)serialized is not allowed: Microsoft.Exchange.Data.Directory.DirectoryBackendType

If you experience this issue, contact Microsoft support to obtain the fix as documented in KB2988229. This fix requires Exchange Server 2013 Service Pack 1 (SP1) or Cumulative Update 5 (CU5).

The fix is not required if you already have a hybrid deployment and do not have a need to run the HCW again.

If you currently have an Exchange 2013-based hybrid deployment configured, you will not notice any issues unless you rerun the HCW as part of updating or managing your existing hybrid features. Unless you need to reconfigure your hybrid deployment, you can simply wait for the next update of Exchange Server 2013 (Cumulative Update 6) to correct this issue with the HCW.

Microsoft also provides an FAQ here which should cover any concerns or confusion people may have about this issue.

If for some reason you are unable to acquire the fix from Microsoft Support you could use the steps documented by Steve Goodman here to manually set up a hybrid configuration. However please pay attention to Steve’s warnings and caveats about this approach.

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. Mark Bayliss


    We have this issue. How do we go about installing Exchange 2013 then as we cannot do this.



  2. Paul Middleton

    Not sure if anybody else has had a similar problem but this same error occurs during a new install of Exchange 2013 with SP1 when you already have Exchange Hybrid already setup in your environment. This essentially means you can’t currently install any further Exchange servers (or at least in my case upgrade your exchange server from 2010).

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