How to Log a email response which is send by the case creator who has submitted the case from community form?

Hi Community  I have created a community support form for the network users who are facing the issue with login activity. so when the network user submits the form the case gets created in the case object and the email sent by the case owner /support agent are gets logged against that case record.  But when it comes to the network users who sends a response to the email of the support agents I want to log that same email against that case record in salesforce.  I tried to implement this solution using  Email -to- case salesforce functionality but I did not want log a case using email to case just wants to log a email.  I also tried the Einstein Activity Capture but it is not available for the case object.  please suggest me any solution  Thanks in advance ! @Community Contributor @Community Cloud Consultant Cert. Prep @Service Cloud Users@Saleforce Cloud