How to add a shared mailbox in Office for Windows. This is not generally recommended except for administrative assistants or similar circumstances.
"Before you can become a delegate, another person must grant you delegate access to a Microsoft Exchange account. You may receive an email notifying you that you have been granted delegate access to someone's calendar, contacts, or email. To access the items for which you are a delegate, you must add the person who granted you access to your People I am a delegate for list. When you want to stop being a delegate for someone, you need to remove the person from the list." (Source: Office support article).
In Outlook, Click on the File menu.
Click Account Settings then Account Settings...
Select account to edit and click Change
From Change Account window click More Settings...
Click Advanced tab. Click Add.
Enter email address of mailbox to be delegate for and click OK
Click OK until back to normal Outlook window.
May need to close and re-launch outlook for mailbox to load.
Need more help?
If this article does not help resolve the issue, please submit a ticket.