Sony Ericsson P910

Hey everyone I just got my P910a and its great. The problem I am having is when I go to a secure site it gives all that show up is html text and the the web page. I'm actually trying to access my exchange server. I know the treo 650 lets me go to that website. Do I need to get a certain plug in or what. Also my phone lets me choose Cingular -mms or express to access the internet. Which one is better.

thanks