To remove a shared mailbox from your personal Outlook profile, first open the Outlook client. Then click 'file' in the top left and click the drop-down box under 'Account Information' and check to see if the mailbox you would like to remove is listed underneath your own. There are no additional mailboxes in the example shown below but this is where they would be shown.

Once you have verified the name of the shared mailbox, once again click 'file' in the top left to navigate back to this page and then click 'account settings' and then again, 'account settings' from the drop-down options.

A new dialog box should then open. Check to see if the shared mailbox is listed as a separate line to your personal email address. Please select it if so and click 'remove' and then 'yes' from the following pop-up confirmation. An example of this box is provided below, highlighted in yellow where the additional mailboxes would be.

Once this step is complete, double click your own personal address in the list. A new dialog box should pop up, please select 'more settings' and then the 'advanced' tab. You may see the shared mailbox you are trying to remove in this window and if you do, please select it, and remove. Then click apply and ok.

Once this is applied, please restart Outlook. This should fully remove a shared mailbox from your personal Outlook profile.