Check if email has been read or not in Outlook (without tracking)

Hi -

If they have not put tracking or some 3rd party software is there any way that a user can tell if another user has opened their email (Within Outlook)- This is within the same Exchange organisation. I also have access to the specific mailbox in question which needs checking whether it read an email sent from another user. I said to my client it was possible without enabling the options, but maybe there are hidden properties or logs that i am not aware of.

Thanks
D