I don't have one, I use my POP address that my ISP provides. But if I activate a BB address does it just use the BB server and bypass my ISP and pc entirely? I would think it would be an email version of the BB Messenger option, right?

Are you using Desktop Manager to redirect your email account? If so, you can use 1 redirected account or 1 BES account, but not both. The BES account will take over.

Can you access your POP mail from the web? If you can then configure your BIS account to access it.