MS exchange server 2003 integrating with existing Webmail

Dear all,

I have a webamil account for all our existing users and now i had installed a Mail exchange server. I need to instegrate my exchange server with my webmail. I mean all the mails i am sending from outlook -> exchange server -> webmail.
Any mails from webmail -> exchange server -> outlook. Where and What settings i need to do in my Mail exchange server.

Where I need to specify my webmails Pop3 and SMTP IP or domain name in my exchange server. If any link pls specify to my mail rakeshhaari@gmail.com.

Thanks and Regards,
Rakesh.