Well, After a long time out, with a lot of work, I had time to look at myself and wrestle with the different types of high availability that Microsoft Exchange gives us 2007 to date. Unlike Microsoft Exchange 2003, This version, brings more possibilities to have a high availability of our mail server, having different methods, some cheaper than others and more or less complex. In principle, we have: CCR (Cluster Continuous Replication o Replicación Continua en Clúster) SCC (Single Copy Cluster o Clúster de Copia Única) CSF (Local Continuous Replication o Replicación Continua Local) SCR (Standby Continuous Replication o Replicación Continua en Espera)