Mail Security must be installed on all active and all passive nodes of a cluster.
Only one Clusterservername (Clusterserverinitials) can run on any cluster node at any time. If two Clusterserverinitialss try to run on the same node, the results are undefined.
Ensure that the following requirements are met before you install Mail Security on an Exchange cluster with one or more passive nodes:
There must be an available passive node to fail to. Multiple failovers are supported only if multiple passive nodes are available.
Mail Security must be installed with the same configuration and in the same locations on all nodes of the cluster.
Mail Security checks for the presence of a cluster environment during installation. You are prompted to register a cluster resource DLL (SMSMSEClusterResource.dll) if the installation is running in a cluster environment. This DLL must be registered on only one of the cluster nodes.
Mail Security runs on all of the nodes (even passive nodes) immediately after installation. After the first instance of the cluster resource is configured, the service runs on only the active node(s).
Clustered continuous replication
You do not need to configure a cluster resource for this type of cluster.