Note: Before you can use a shared mailbox, the Microsoft 365 admin has to create it and add you as a member.
Adding a shared mailbox
After your admin has added you as a member of a shared mailbox, close and then restart new Outlook. The shared mailbox should automatically display in your Folder pane.
If your admin only recently added you to a shared mailbox, it may take a few minutes before the shared mailbox appears. Wait a bit and then close and restart the new Outlook again.
How to find the shared mailbox in the folder pane
In the folder pane on the left, locate the Shared with me folder. Click the folder to expand it. Your shared mailbox is a subfolder under Shared with me. When you select the name of the shared mailbox there, it will expand to show the standard email folders, such as Inbox, Drafts, and Sent Items.
How to manually Add a shared mailbox
Note: Before you can use a shared mailbox, the Microsoft 365 admin has to add you as a member.