Microsoft Active Sync problem/question

Just as a preface, i am a long time reader first time poster.... I haven't seen anything specific in regards to this question but maybe one of you can help me out. I am planning on getting the new iphone 3g for work and will be taking advantage of the microsoft active sync to access my work email. In order to using microsoft active sync do i need to sign up for an enterprise plan or can I move forward with just a typical plan and data and minutes and all that other semi-overpriced stuff? I have heard yes you do need enterprise and no you don't if you are just using it for email (just like any other phone and plan on att)

anyone, anyone?

thank you in advance.....