2000 – 2007 Migration Path

We are moving to Exchange 2007 with CCR mailbox cluster and a seperate front end, with an ISA box in the DMZ to route in webmail. The front end will have all other roles on it apart from the mailbox role.

I will have 4 servers, 2 on the backend with CCR, and two front end. Now I do not know is it best to load balance over both the front end, or keep it in a failover role like the mailbox servers.

We currently have 1 exchange 2000 server on windows 2000 with a PC in the DMZ to route webmail.

Once I have the front, back and DMZ ends all setup, what is the best way to start the migration accross?

I seem to remeber somthing that you have the 2007 handle the receiving and sending of email, with a connector to the 2000 system? Is that right or have I got my head on backwards?

Just after the smoothest way to migrate the mailboxes across.

Thanks

Dave