Follow these steps to open a group account you belong to as a shared mailbox in Outlook 2016.
1. In Outlook 2016, click Mail in the bottom-left corner of the window (if necessary).
2. Right-click your account name (i.e., email address) in the folders pane on the left side of the window and select Data File Properties from the menu.
3. Click the Advanced button in the Properties window.
4. Then, click the Advanced tab.
5. Click the Add button to specify a shared mailbox.
6. Type the email address for the group account in the Add Mailbox window and click OK.
7. The account now appears in the list of additional mailboxes. Click Apply and then OK (twice).
The shared mailbox now appears in your list of email folders under its own heading allowing you to view, send, and manage emails for this group account.
If it does not appear right away, exit the Outlook App and then open it up again. This refreshes the connection to the server.