Exchange 2010: Mail-enabled Public Folders not receiving mail

Just upgraded our Exchange 2003 infrastructure to 2010 and get reports from the users that our mail-enabled public folders are not recieving mail. They are failing with the following error. #554 5.2.0 STOREDRV.Deliver.Exception:ObjectNotFoundException; Failed to process message due to a permanent exception with message The Active Directory user wasn’t found. ObjectNotFoundException: The Active Directory user…