======Adding A Secondary Mailbox to an Existing Account in Outlook 2016======
=====Windows=====
  - Load Outlook
  - Click on **File**
  - Select **Account Settings->Account Settings...**
  - Your email account will be listed, double click on this
  - In the next window that pops up select **More Settings…**
  - Click on the **Advanced** tab.
  - Click on the **Add…** button
  - Enter the ''username'' in the **Add mailbox** field
  - Click **OK**
  - Click **Apply**, Click **OK**
  - Click **Next**, click **Finish**
  - Click **Close**

This new mailbox will show up as a new Mail folder under your existing mailbox.
=====Mac=====
  - Load Outlook
  - Navigate to **Tools** > **Accounts**
  - Select your Exchange account on the left
  - Click **Advanced**
  - Click **Delegates**
  - Click on the plus ("**+**") sign below the "Open these additional mailboxes" pane
  - Enter the username of the mailbox you are trying to add
  - Make sure the mailbox is selected and click **OK**
  - Click **OK** again to close the Accounts window

This new mailbox will show up as a new Mail folder under your existing mailbox.