Our organization sets up "shared" mailboxes by just creating a regular mailbox and then giving people Full Access in the ecp/exchange admin. It then automaps to their Outlook client. But we are running into the bug where emails sent to that address marked as private, will be invisible. Users can see the count ("Inbox 6"), but not the actual email in Outlook client (only in OWA). The only "fixes" I can find involve a system using Delegate settings. We do not do delegates. No one in our company is a listed delegate nor are these "shared" mailboxes even attached to a client as a standalone where Delegate settings could be managed. Any other resolutions for this?
SnapOverflow
Based on your description, the "shared mailbox" is normal mailbox, so you could configure it in the Outlook client and add the users who need to see private emails as delegates with Delegate can see my private items selected. I have tested in my lab, here's a screenshot for your reference(user01 has usr02's full access permission):
Steps:
Open user02's mailbox in outlook client.
Open account setting, click delegate access, add user01 as a delegate, edit permission and choose "Delegate can see my private items"
Then the user01 can see the private mails in user02's mailbox.