Hiding mailboxes in GAL

We have 3 HR mailboxes. HR-Syd, HR-Mel and Hr-Bne. HR staff want to be able to view these 3 HR mailboxes for external mail. However, we also have 3 distribution lists with very similar names HRsyd HRmel and HRBne. In order to prevent confusion amongst internal staff, we want to be able to hide the 3 HR mailboxes. What we have found though is, if you hide the mailboxes and then try to open them within outlook, you can’t because they can’t be found in the GAL. A workaround we’re currently looking at is renaming the mailboxes so that in the GAL, they won’t be right next to the distribution lists, hence minimising any chances of an internal user sending to one of the HR mailboxes instead of the distribution list. Any thoughts? Is this confusing enough?!