Set up for shared mailboxes in Outlook Online
If you want to connect shared mailboxes from Outlook or you or your coworkers have granted access for their mailbox to other users, please also add these permissions:
Request API Permissions
Choose Microsoft Graph and then Application Permission
Request permissions for the following resources:
MailboxSettings.Read
Request API Permissions
Choose Microsoft Graph and then Delegated Permission
Request permissions for the following resource:
Mail.Read.Shared