1. When end-user replies to the CSR email which was triggered before from the email interaction case gets updated in the existed interaction case if the CSR doesn't wrap-up the interaction case.
2. Let's consider that CSR wrapup the interaction case and end-user replies to the CSR's email, then a new interaction case gets created and the email thread is updated in the newly created interaction case. When you open the previous interaction case which CSR has done the wrapup, there as well the email thread got updated, but as CSR has done the wrapup the interaction work object status gets changed to Resolved-Completed.