Ajmal, have you already read the <a href=”http://www.apple.com/iphone/enterprise/integration.html”>iPhone in the Enterprise</a> documentation from Apple? If not, that would be a good place to start.
Here are a couple of other resources you may wish to read:
<a href=”http://msexchangeteam.com/archive/2008/07/11/449196.aspx”>iPhone 2.0; Welcome to Exchange!</a>
<a href=”http://www.theiphoneblog.com/2008/07/13/walkthrough-exchange-activesync-on-your-iphone-20/”>Walkthrough: Exchange ActiveSync On Your iPhone 2.0</a>