I’ve been working with the Microsoft team on several issues I have faced with my Exchange Hybrid deployment.
Most recent issue: HCW Serialization Error
Today I am informed that Cumulative Update 6 for Exchange Server 2013 was just released.
Cumulative Update 6 for Microsoft Exchange Server 2013 was released on August 26, 2014. This cumulative update resolves a list of issues.
Source: http://support.microsoft.com/kb/2961810