This article provides instructions to manage mailbox delegates on New Outlook (Windows).
Click File tab
Select Account Settings > Delegate Access.
Select Add. Then type the person's name and press Enter to search for it.
Select the person's name, then select Add, and then select OK.
Under Delegate Permissions, set these five options to None: Calendar, Tasks, Inbox, Contacts, and Notes.
Selecting None for each of these options gives the delegate the basic ability to send messages on your behalf, but nothing more. You can grant the delegate additional permissions (such as the ability to see your calendar or inbox) by selecting Calendar > Author or Inbox > Reviewer, for example.
To send an automatic message to your delegate, select the checkbox Automatically send a message to delegate summarizing these permissions.
Select OK.
Select the back button to return to your Mail.
Click File > Open & Export > Other User's Folder.
Tip: To avoid this step in the future, see the instructions on how to add another person's mailbox to the Folder Pane in the Add another person's mailbox to your profile section of this article.
In the Name box, enter the name of the person who granted you Sharing or Delegate Access permissions, or click Name to select from a list.
In the Folder type list, click the folder that you want to open.