After deploying CU6 to Exchange servers there is no way to perform activities on Exchange Online (cosidering hybrid deployment). I noticed that there is a fix for it in http://support.microsoft.com/kb/2997355 but it seems that it doesn’t do the trick. After installing CU6 file which is altered in the script cannot be found (RemoteDomains.xaml).
Also after installing CU6 I've noticed issue with IMAP and Thunderbird. It seems that commands like move are interpreted by the server as bad commands (error 12).
Did you encounter with any of those problems? Do you have/recommend any workaround or fix?