If you have access to a Shared Mailbox, you may want to check that mailbox on your mobile device. Unfortunately, the way a shared mailbox is set up prevents us from adding the mailbox to the mail applications installed on our mobile devices. So, in order to access these mailboxes, you'll need to access them via the web at outlook.office.com. First, you'll need to enable the shared mailbox in your web portal account on a computer, and then log on via your mobile device.
Sign in to your account at outlook.office.com on your computer (you won't be able to complete this via the web browser on your phone).
Right-click your primary mailbox in the left navigation pane, and then choose Add shared folder. (Your name is on your primary mailbox.)
In the Add shared folder dialog box, type the email address of the shared mailbox (it should appear below as it searches the global address book), select the mailbox, and then click Add.
The shared mailbox displays in your Folder list in the menu bar on the left. You can expand or collapse the shared mailbox folders as you can with your primary mailbox.
Now, when you log in to outlook.office.com on your mobile device, the account should remember that you've added this mailbox to your account, and display in the list of mailboxes in the menu bar.