I'm running an Exchange 2013 on Windows Server 2012. The clients use Outlook 2007 and Outlook 2010. For every user mailbox i've set the access rights for their calendar folder to User: Standard AccessRights: Reviewer
If i display more than 6 shared calendars, every newly displayed calendar shows the "could not be updated" message. There is no difference in what shared calendars i open. After i close Outlook and open it again i can select up to 6 shared calendars again (even those, that showed the "could not be updated message" before)
By running netstat -n in the command prompt i've noticed that for every shared calendar that is added in Outlook two more tcp connections to the port 443 of the Exchange server are established. When i initially start Outlook i've got 4 tcp connections to the exchange server. After displaying 6 shared calendars i've got in total 16 tcp connections to the exchange server. If i add one more shared calendar there are no additional tcp connections opened and the message "could not be updated" is displayed.
I turned on Logging in Outlook, examined the logfiles and found an XML response from the Exchange Webservice with the <ResponseCode>ErrorNoFreeBusyAccess</ResponseCode>
It looks like as soon as the maximum tcp connections from the client to the exchange web-server is reached Outlook communicates through an existing connection which results in an Error.
Any help appreciated