Do you have a BlackBerry data plan with your cellular provider? If not, no email. Is your BlackBerry displaying GPRS (all capital letters) next to your signal strength indicator? If not, no email. Have you configured the carrier provided BIS email address? If not, no email.
Just buying a BlackBerry does not give it the ability to send and receive email. You much configure it to do so. There should have been instructions in the box on how to do this.