ACL problems

[Robert Schmid]

I have one user with complete access to another users mailbox hierarchy. 
I dumped the entire mailbox database using ctl_mailbox -d.

I deleted two lines for a couple of shared directories and double checked
the permissions for the two users.  I could see nothing that would allow
the one user to see the other.  Also there appears to be a folder 'Other
Users' under which the other user's directory is seen. There was no sign
of a mailbox called 'Other Users' in the database.

I then rebuilt the mailboxes database from the text file.  As expected the
two shared folders were gone but the one user can still see the other
user's hierarchy.

Where else should I look to find out how this user is getting access to
these other mailboxes?