How to add a second exchange server aditional ?

Hi: Our Enterprise has a domain hosting and email exchange with Cbeyond ,and we want to install an aditional exchange server email in our enterprise for the intranet ,we would like also to received and send email to the exterior in this internal server email
How to do that if we already have an email hosting service ,I mean how to sinchronize our second email server with the server of cbeyond ???
regards