Using labels is a way to structure your messages work flow in iController.
When using labels (e.g. a label per user, a label 'to discuss'), you can make it a habit to only use the label folders as your inbox folders.
After labeling an email (how?), you can find this message in the correct label folder under 'labels' in the left menu. Every email that didn't get a label (yet) will be collected in the last label folder 'without label'.
When using the labeling as instructed above, the general 'inbox' folder will be a useful collection of all unprocessed messages (= emails that aren't linked to a debtor, how?).