Today, April 2^nd 2013 Microsoft released Cumulative Update 1 (CU1) for Exchange Server 2013 RTM. CU1 is an important release since it offers the possibility to integrate with an existing Exchange Server 2007 or Exchange Server 2010 environment (this was not possible using the original Exchange Server 2013 RTM release). The official version of CU1 is build 620-29.

Furthermore there are many, many bugfixes in CU1 (several thousands, but these also include typo’s and language issues) but also some new additional features:

• Address Book Policy Routing Agent – especially important for hosting environments. For more information regarding this check out Address Book Policies, Jamba Jokes and Secret Agents;
• Group membership management by groups – a long awaited feature that was also available in Exchange Server 2007 and earlier;
• Access to Public Folders via favorites;
• Exchange Admin Center (EAC) enhancements;
• Improved probes, monitors and responders (part of managed availability);
• Optimized Get-HealthReport;
• Exchange 2013 Management Pack for SCOM;
• Auto-reseed supports bitlocker encrypted disks;

CU1 is the first update as part of Microsoft’s new servicing model. This means that CU1 is approx. 1.3 GB in size, it is not an update on top of Exchange Server 2013 RTM but it’s a full version. When deploying there’s no need to install Exchange Server 2013 RTM first, you can start directly with deploying CU1.

For more information check out the Release Notes on http://blogs.technet.com/b/exchange/archive/2013/04/02/released-exchange-server-2013-rtm-cumulative-update-1.aspx or download CU1 directly from the Microsoft download site: http://www.microsoft.com/en-us/download/details.aspx?id=38176

Please note that a Cumulative Update is not the same as a Service Pack. Microsoft will release a CU on a regular basis, most likely four times a year (once every quarter). For Exchange Server 2013 Microsoft is planning to release Service Pack 1 (SP1), but no information is available at the time of writing.