This useful feature allows a system administrator to share an user’s email Inbox with another user.
The menu is quite simple, you have only 2 options: Creating and Removing:

By clicking each option you will access the corresponding menu:
Creating: This is where a sharing is created. You need to select the account that will be sharing its Inbox folder from the first drop-down menu, and then the account of the user with who you want to share in the second drop-down menu.

Finally clic on Sharing to share.
Attention! Sharing an Inbox folder will also share all the sub-folders contained in it, including system folders (Sent, Spam, Drafts, Trash). |
Removing: Here you can remove a sharing for an user’s Inbox.

In order to remove a sharing between 2 accounts, you only need to enter the email address of the account that is sharing its Inbox folder.
Attention! A folder manually shared by an user through the webmail will not be removed using the Removing option from the Sharing module. |
See the video below for a practical guide