Exchange Server 2003 does not by itself support geo-clusters. Clustering requires that both nodes be on the same public subnet for public communication, and the same private subnet for heartbeat communication. Additionally, the quorum and shared Exchange data is located on shared storage.
<a href=”http://technet.microsoft.com/en-us/library/bb123612(EXCHG.65).aspx”>Deploying Exchange Server 2003 in a Cluster</a>
Partner solutions may help you to setup geo-clusters. You will have to rely on these partners to get documentation and support.