I don’t know how much this impacts standalone Exchange 2013, but
hybrid/mixed installs with Exchange 2007 appear to be having issues.
(from the bottom of
http://blogs.technet.com/b/exchange/archive/2014/08/26/released-cumulative-update-6-for-exchange-server-2013.aspx
Issue Reported: Ryan reported on my blog that they are facing an issue
with CU6 in exchange 2007 mix mode here. Any confirmation will be
appreciated.
http://msexchangeguru.com/2014/08/28/e2013cu6installation/
Following issue reported.
===================================================
Do not install this CU6 if you have a 2007COEX with EX13. Were having
major issues with databases flapping. This is due to EX07 mailboxes
talking to EX13 mailboxes. MS are aware of this and working on a fix now.
@PrabhatNigam – Yes, we became aware of this issue earlier today. This
happens when a 2007 user attempts to access a delegated mailbox that is
on a 2013 server. This issue is being tracked by KB2997209, that is
still being published.
The EXPTA {blog}: Don’t Deploy Exchange 2013 CU6 If You’re a Hybrid
Customer:
http://www.expta.com/2014/08/dont-deploy-exchange-2013-cu6-if-youre.html
