When you're managing multiple mailboxes in Groove, you have the option to view these as a unified mailbox or as separate mailboxes in your left navigation list. 

Admins for the account can access this preference under Settings > Conversations > Preferences. At the top of the page there is a dropdown selection for "separate inboxes" and "a single inbox". 

If you opt for "separate inboxes" then beneath that preference you'll see a second preference appear that allows you to add an "All Inboxes" section above your separate mailboxes, which allows you to have the best of both worlds -- an available unified view at the top of the list, as well as your separate mailboxes listed underneath. 

There's no right or wrong way to configure your Inbox, it just depends on your workflow and the needs of your team. 

Here's what each option looks like in action:

Single Inbox Unified View

Separate Inboxes

Separate Inboxes With "All Inboxes" Section

(Note that these preferences are applied for all users in the account. These settings cannot be configured individually for different users.)