When we set regarding on a email in Outlook with Dynamics 365 App for Outlook, or send a email by dynamics email activites. only the send email and is replys are track in Dynamics in the element regarding, a reply on the Customer reply of the tracked email wans't not track automaticaly. We need to do manually on the reply of the reply to set regarding in order to get it track in Dynamics in the Case by example. We would to get all email how follow the first with in the same chain are be track automatically. So the reply and the follow on with the same subject go in the case for the example.