Encrypted emails - need to understand process

Let me start by saying I am NOT a Lotus Notes guy.  I used it about 10 years ago, but never dealt with the back-end admin of it.  I'm an Exchange guy (Go ahead and hiss!)

Working with a client that had Lotus Notes a year or so ago.  The company needs to retrieve emails from certain mailboxes due to litigation.  Those users are gone, and so are the Notes admins.  A third-party came in to try and help, but they said the mailboxes are encrypted.

So I've done some research.  It sounds like Notes lets the users encrypt individual messages (And sounds like there's an option to encrypt everything coming in as well, as a user option.)  So if a user turns this on, and sends all encrypted emails, are we screwed if we don't have the user's Notes ID file?  Everything I've read says creating a new ID will just render the encrypted messages lost basically - understood.  

I guess coming from Exchange, where technically an admin can gain access to anyone's mailbox and access emails no matter what, this is foreign to me and I want to make sure I truly understand what's going on here and that there's NO way to get into the mail without the original ID files.