we are on exchange 2007 and outlook 2010. I have issue with one of our directors calendar, it is delegated to executive assistant and she does most of the calendar management. For some calendar meetings if they want to check other attendee details they are getting message "Attendee list unavailable" . This happening for both director and his assistant, even I tried his mailbox from my outlook by mapping as a mailbox, resulted is same. We tried all possible options including deleting mailbox and recreated in a new cluster. Any suggestion? Thanks

I have the same problem here. I got 10 mailboxes that gives me this error. we are on exchange 2007 with outlook 2007 Also tried making new mailboxes and setting the delegation again. when i run get-mailbox -identity <user> | FL i get this back: RecipientType : UserMailbox RecipientTypeDetails : RoomMailbox