With Outlook 2016 most shared mailboxes will automatically be added to your outlook client. If the mailbox has been around for awhile it needs a little bit of help. This is the guide I send to users to add or remove a shared mailbox.
- Select File in the upper left corner of the screen.
- Select Account Settings > Account Settings.
- Select your primary account and then double click on it
- Click More settings
- Select Advanced tab
- To add a mailbox, Select Add and type the email address of the mailbox as it appears in the address list
- Remove the mailbox select the mailbox you are wanting to remove
- Select OK
- Select Next
- Select Done
- Select Close
- Restart Outlook and see if the mailbox is Added/removed
Tip - If you don't find your mailbox in the account settings contact your IT department as this a new style mailbox and you will need your permissions removed for it to be removed from Outlook.
This post is a "just for documentation (JFD)" post which I use for my referance, but I have made public as it may be useful. I put less time into these posts as they are my reference. If you would like more information or some help post a comment, and I can see what I can do.