You can do both, but be careful if it is a personal BB and you allow your company to put their IT policy on it to connect to their BES. It can restrict what you do and make it difficult if you leave the company.
You can just forward a copy of the business email from the mail server to the
![[email address]](http://www.blackberryforums.com/?emailimage=02e362eeb788693dfe5bddbbcddac4ca)
address and be good to go (if the company allows forwarding outside their network).
I am sure if you search the forum there are plenty of threads on setting it up.