Log in to your carrier's BWC/BIS site and set up the POP email accounts that you want delivered to your Blackberry. Setup BES normally. That's pretty much all there is to it. If you scroll to the headers of an incoming email you can see if it arrived via desktop (BES) or web client. You can choose whether to originate a new email or reply via BES or BWC/BIS if you scroll to the headers of the email.
Using Both BES and BWC
