Microsoft has released Cumulative Update 1 (CU1) for Exchange Server 2013 RTM.

This is a significant update for two reasons. It is the first release of a CU under Microsoft’s new servicing model for Exchange Server 2013. And it is the minimum version of Exchange 2013 required for on-premises co-existence with Exchange 2007 (SP3 UR10) and Exchange 2010 (SP3).

Some important points to note:

  • Cumulative updates are a full server upgrade, similar to service packs for previous versions of Exchange, not a minor update like an Update Rollup.
  • Exchange 2013 RTM CU1 includes an AD schema update and some AD permissions changes. Read the release notes for full details.
  • There is some preparation required for your existing OAB configuration to ensure the new Exchange 2013 OAB that is created does not cause unwanted network traffic.

Aside from the co-existence support and considerations there are also some improvements for existing Exchange 2013 RTM environments.

Download Exchange Server 2013 RTM CU1 here.

Deployment Steps: refer to Installing Cumulative Updates for Exchange Server 2013.

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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


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