We have an inbox that is shared by a lot of users, it isn't setup as
the actaul email account in Outlook is is just and extra added mailbox
the users can view. When one company sends email to this inbox we
cannot see the messages. They are in there and show in the total
number of unread messages, but I can't see the message.

I have installed Outlook on a spare machine and set this mailbox up as
the actual email aco**** and then I can see the messages. When I open
them I notice is says "Please treat this message as private" at the top
of the message. I think it is a combination of the security on this
message that was sent (possibly done with Microsofts IRM service?) and
the fact that this inbox is just an extra added inbox, not the main
email account.

I am not sure what to do about this. Would I need the email sent with
different security or is there a way to get these messages to show up
in the shared mailbox?

Thanks,
Teresa