Clutter

Clutting process allows to remove empty folders and any thread data from emails such that you don't need to review the same emails over, and over.

How to remove threads and empty folders:

1- Open your box and click the "Cull" tab, then click on "Clutter". 

2- Select email threads and empty folders and click on the "Declutter" button

For more details about de-threading, click HERE