have person log into their blackberry account and create a filter for that email address. Put the filter to NOT SEND things "from: xxxx" being that email address that is sending and coming to the BB as new messages.
in the mail application, go to options, e-mail settings, then press the menus again and highlight folder redirection. At this pont you will see "mailbox". click on it and it will open up and you can check the folders that you want re-directed to the bb.