Journaling is working - however - How do allow it to to accept messages only from the Microsoft Exchange recipient?

I created a new user account called Journal Manager (with an email address:  journal@xxxxx.com).
I have enabled journaling.
The journaling reports are sent to journal@xxxxx.com

The problem is, when any user drafts a message and clicks on the To: button, the newuser "Journal Manager" appears in the global address list. I do not want any user to send e-mail to the journal@xxxxx.com address.

In the set up section, it says:

Configure the journaling mailbox to accept messages only from the Microsoft Exchange recipient Journaling mailboxes receive journal reports from the Journaling agent. To maintain the integrity of the journaling mailbox and prevent fake journal reports and other messages, it should be configured to receive e-mail only from the Journaling agent. The Journaling agent delivers journal reports to the journaling mailbox by using the Microsoft Exchange recipient, a system mailbox that isn't visible in the global address list (GAL). For more details about the Microsoft Exchange recipient.

It seems to me, there is no "system mailbox", just a regular user mailbox.
Under the e-mail addresses tab for Journal Manager, there are two addresses:  JournalManager@myserver.local and
JournalManager@xxxxx.com

Thanks for your help.