Scan of identical files

hi

How is the standard behavior with a sandbox with regard to identical files? I only see that sometimes identical files sent to multiple recipients are scanned for each recipient. This does not really make sense and makes the whole only slowly. Under the menu general gives an option "Reject duplicate file from device" what exactly happens when I turn this option on? Then the files, which have already been scanned with the identical hash value are no longer scanned? That would make sense Thank you for your feedback