2 Domains, 2 Exchange 2K Servers, One Site??

[bchasse]

I have a client that has two Netwoks connected via Point2Point VPN, They are setup to trust both ways. The Domains are different, however the goal is to set up an exchange server in Domain X to be a backup to the one in Domain Y (Production Machine), all server are running 2K and exchange 2K.

Thanks