If you have chosen to switch over to the new version of Outlook on a Windows system, shared email mailboxes will automatically be added. Here is how to find them.
1. Switch to New Outlook. Please consult this article about how to switch from Old Outlook to New Outlook for more information.
2. When using New Outlook, expand your personal account folders and look for the “Shared with me” folder near the bottom. Once you expand the folder, all your shared mailboxes should be there.
3. If you do not see the “Shared with me” folder in your list, you may need to ensure your Outlook is the most up-to-date version. You can download this version at portal.office.com using these instructions.
Here's how to send email from your shared mailbox address on New Outlook.