I have a Exchange 2003/Outlook 2007 user, who is not able to open shared exchange 2010 mailbox calendar. Error says " The connection to the Microsoft Exchange server is unavailable. Outlook must be online or connected to complete this action " The issue started after the shared mailbox was migrated from Exchange 2003 to Exchange 2010.... Exchange 2003 user has "Author" permission on Exchange 2010 mailbox calendar... Please suggest