To view a delegated mailbox please follow the steps below:

•  Log into webmail as usual via https://outlook.office.com
• Click your initials (or profile pic if one has set on your mailbox) in the top right-hand corner of the browser window.
  
•  Click “Open another mailbox”
• In the window that appears, start typing the email address of the mailbox you would like to access and then click open.                                                         
• The mailbox will open in  a new tab in your browser.