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on the side bar click the more apps icon
Right Click on folders and click pin
You can now view the shared inbox folder
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Click the 3 dots at the bottom of the screen and select Folder
You can now view the shared inbox folder
Outlook on the web
Use this method if you want to view and manage the email for the shared mailbox in its own browser window. This method also lets you receive notifications of new items in the Inbox of the shared mailbox.
Sign in to your account in Outlook on the web.
On the Outlook on the web navigation bar, click your name. A list appears.
Click Open another mailbox.
Type the email address of the other mailbox that you want to open, and then click Open. Another Outlook on the web session opens in a separate window, allowing access to the other mailbox.