We had a very similar issue with emails on closed cases. What we wanted to happen is the following: when an Email is regarding a case that is already closed, take away the relationship between the Case and the Email, and create a Queue Item for that email, for it to show up in email queues again. We achieved this with a Cloud Flow.
Now that the email is back in the queue, the managing user can decide whether the email should actually be linked to the former Case, or that a new Case should be created.
Now, the difference with your story is, that we actually use the Resolved statecode of a Case. The Case is closed, and however a new email is received, it won't open up the case again (it will just be listed in the Timeline). Furthermore: Our SLA success criteria have already been met at this point, so this situation won't mess with the SLA Resolution times.
I think the root of your issue is: how can you prevent an incoming email to change the status of the Case. Cause if you can take that step out, you can work with a flow like mine to decide if Resolved time is greater than 48h ago, and decide from there what to do with the status of your case, and the regarding of the email.
I'm well aware that I'm not providing a full answer to your question, but it may put you on the right path. I'm also happy to help further if that could help.Regards,
If you've found this thread useful, dive deeper into User Group community content by role