Xpressmail will use data. It is not required to have a data plan, but you will be charged $0.01/kB. I do not recommend using Xpressmail without a data plan.
If you don't get much email, then you could possiblly pay less than the cost of the data plan. But if you manually hit, send/receive, even if you have no new mail, you will still be using a few kB of data. And the point of Xpressmail is to automatically send the mail to your phone without having to manually hit receive. So if you get a lot of spam, you will be paying a lot and won't have control over when your phone uses data.
Either get a data plan, or do not use Xpressmail and configure your phone to not use push mail or automatically check for mail. Configure your phone to only receive mail when you manually press send/receive.
Thanks, I'm still not sure if $30.00 for a data plan is worth it especially when I have the $15.00 plan on my daughters blackjack and it works just fine. And I only got that because she had it on her old phone before I gave her my BJ1 to upgrade to my new BJ2.