How can I see who has access to a shared inbox in the new version of . . . This is a new arrangement in the updated version of Outlook Check Permissions : Right-click on the shared mailbox and select "Properties" or "Permissions " This will show you a list of users who have access to the shared mailbox and their respective permission levels
Get a List of Mailboxes a User Has Access to in Exchange Microsoft 365 Use the Get-MailboxPermission cmdlet to get a list of permissions assigned to a mailbox Open a PowerShell console and connect to your on-premises Exchange Server or Microsoft 365 (Exchange Online) The command below displays a list of users having permission to access the specified mailbox:
How to Detect Who Was Accessing Shared Mailbox in Office 365 - Netwrix Open Exchange Administration Center → Navigate to "Compliance Management" Auditing Click "Run a non-owner mailbox access report" You will get the report on non-owner access to all mailboxes with enabled auditing over the past two weeks