We have an Exchange 2010 environment, and we have the servers distributed on 3 regions/datacenters, all of them are installed in the same forest.No cross forest.
The issue is with a single user mailbox that which ever region server it is on, it can't see free/busy for other people that are on the other 2 regions. Issue is ocuring in Outlook and OWA as well. All servers are configured the same, we checked the EWS, IIS logs, no error.
The error that the user's get in OWA is "The Attendee server couldn't be contacted. (Error code:5016)".
We even create a new mailbox and connected the AD user to this new one, but the issue still persists.
Does someone have any suggestions/ideas what can be the cause?