I read through most of the topics to get the information I needed. I just need to verify what I found...

I have a BB 6230 on T-mobile.
I have GPRS enabled in my account (Not any Blackberry Internet plan)

I did add my apn to the TCP stack ( I have OS 4.0)

I still can't browse the internet.

From what I found this is due to the fact that I don't have a Blackberry Internet plan, only regular GPRS enabled. Is this correct ?

So what's the diff. between the GPRS and BB Internet Plan ? From a network point of view... ? Are some addtional ports open perhaps ? Thanks in advance for the information.

No way around it, if you want email or web on your BB you will need a BlackBerry Data Plan to do so. Most likely has to do with BlackBerry devices connecting through BES and BIS servers on the back end. This holds true for all BlackBerry providers.