This guide will be based upon the web version of Outlook in Office 365.
To delete multiple emails in Outlook or Office 365, you must first login.
Please note: You must have permission to the mailbox to open it, so you will not be able to open anyone's mailbox.
You can follow our guide to logging in:
Once you have logged in and successfully navigated to Outlook, you will see this screen:
Once here you will need to click your name in the top right corner:
It will bring up this screen:
Here you can select open another mailbox and type in the mailbox you wish to open:
Once you type in the mailbox you wish to open, it will find it and then allow you to click open.