What are the considerations for Exchange Server 2007 to co exists with Exchange server 2000 and Exchange Server 2003?

• Exchange Organization in Exchange Native Mode· Exchange Server 2007 routing group (DWBGZMFD01QNBJR) is created only for coexisting with earlier versions of Exchange.
• Routing Group Connector is required between Exchange Server 2003 and Exchange Server 2007 (created during setup).
• Exchange Server 2003 computers cannot interoperate with the Unified Messaging server role. Exchange 2003 mailboxes cannot be Unified Messaging–enabled.
• Exchange 2003 Front-ends cannot talk to Exchange Server 2007 Mailbox Server Roles.
• No in-place upgrade on existing Exchange server. Install new Exchange Server 2007 server into existing organization, and move data to new server.