There are quite good number of factors you need to consider before opting for Blackberry or Dopod(any smart phone)
Dopod(any smartphone):
As this runs on WinMobile OS, you can do lot more than messaging, but depends on your requirement and hobby.
You need to have GPRS(or EDGE) connection for this mobile.
So now if you need to configure your inbox, then you need to configure our pop3 and smtps.provided your office offers it.
So to access email is two step, 1. Connect to net 2. Open inbox to check mails(with first time configuration of smtp n pop3)
Blackberry:
This is more a messaging device than a palm device.
It runs on its own OS and so limitation of applications that you can run.
Accessing email is just a push away. We need to take the Blackberry pre connection with a subscriber(in our case AirTel)
And they will do all the configuration and maintaining mailserver sync etc and for you to access email, just push a button.
So validate the requirement and opt for the better device.
Check the below link for detailed comparison of treo and blackberry
http://www.dslreports.com/shownews/36702
Disclaimer : This is purely my comparison survey which i did it with limited knowledge.So it could be wrong or may not be full comparison.If you have any comments, please put forward.