Exchange 2007 Network Implementation in DR Site

I have currently have linux email server in our commpany that we host.

We want to install an exchange server 2007 and put it in a dr site.

right now we have user accessing email from the remote site. most of them use pop3 to access email using outlook express.

my problem is that is is possible to implement exchange in dr site without having any exchange 2007 in our main office?

Thank for your response and more power.