NS8 root mailbox no longer listed once enabled

I have a couple of OS based apps that I was going to load on NS8 that send notifications to root. Under mailboxes, I can see I can forward messages from one mailbox to another user which I do to combine admin and administrator, so I was going to add root as well to the same box, with is disabled by default. But after enabling it, it no longer appears in the list of mailboxes to let me apply the forwarding rule.