In order to see email folders shared by other users, you have to subscribe to those folders. You will be subscribed automatically to your personal email folders. To hide a personal email folder, you have to cancel the subscription.
How to subscribe to personal or shared email folders:
Click theicon in the menu bar. Click on .
The Settings window opens.
Click onin the left pane.
In the Subscribe IMAP folders window enable the checkboxes of the folders that you want to subscribe to. Click on .
Parent topic: Sharing Data