Originally Posted by John Clark
NJ is right (no big surprise there.) If you want to be attached to the BES, then you need the BES plan. If you can pop your corporate account, you're good to go with a BIS plan. On non-BES data plans the Enterprise Activation feature disappears so you can't activate on a BES. If you need that then you have to get the BES plan. It's that simple.
I think both of your responses are incomplete.
A BIS user can utilize OWA to have Exchange mail pushed to their device.
POP is not the only BIS-compatible protocol for non-BES users.
OWA, IMAP, or POP would be sufficient.
I believe the OP has OWA since they have hinted at the fact that they use their web browser to access their exchange mail externally.