To the Original Poster....
dont take this the wrong way, but in the amount of time it would take you to delete the old users data so the new user won't get it.... you could've deleted them completely, added the new person and activated the device.

If you're looking to copy the mail file info from the old person to the new, why not just get your E-mail Admin to copy the mailfile/inbox over on the mail server? You would avoid a lot of JL_CMDR wipes.