We recently migrated from Exchange 2003 to Exchange 2010 (virtual machine on VM Ware) Windows Server 2008R2, we use Citrix Xen app 6.0 to access Outlook 2010, old 2003 server was on the domain for a short time after we migrated. Our issue is some users cannot access 12 out of 100 to be exact, cannot access Exchange 2010 using the Citrix environment. We are getting an error message " Server is unavailable, Retry (nothing happens), Work Offline (Cannot open your default email folders. The Information store could not be opened) Cancel (closes window). Our workaround is to install Outlook 2010 locally on the user's computer. I have called Citrix support and they claim it is a Microsoft issue because if a user launches Outlook on the Citrix server, it works. The Error message pops when Outlook is launching the User Profile. Big points if any one can point us in the right direction to fix this issue.