How to Access a Shared Mailbox in Outlook
Step1: Go to File>Account Settings>Account Settings
Step 2: In the Account Settings window, go to the Data Files tab. Make sure your email address is highlighted and click the Settings button.
Step 3: In the Microsoft Exchange window, go to the Advanced tab. Click the Add button, type in your shared mailbox email address, and click the OK button.
Step 4: Click the OK button in the Microsoft Exchange window, then click the Close button in the Account Settings window. Your shared mailbox will now appear in the Outlook Folder Pane on the left.