If your site serves many Domains, you may want to install several independent CommuniGate Pro Servers and distribute the load by distributing domains between the servers. In this case you do not need to employ the special Cluster Support features. However if you have one or several Domains with 100,000 or more Accounts in each, and you cannot guarantee that clients will always connect to the proper server, or if you need dynamic load balancing and very high availability, you should implement a CommuniGate Pro Cluster on your site.
Many vendors use the term Cluster for simple fail-over or hot stand-by configurations. The CommuniGate Pro software can be used in fail-over, as well as in Distributed Domains configurations, however these configurations are not referred to as Cluster configurations.
A CommuniGate Pro Cluster is a set of Server computers that handle the site mail load together. Each Cluster Server hosts a set of regular, non-shared domains (the CommuniGate Pro Main Domain is always a non-shared one), and it also serves (together with other Cluster Servers) a set of Shared Domains.
To use CommuniGate Pro servers in a Cluster, you need a special CommuniGate Pro Cluster License.
Please read the Scalability section first to learn how to estimate your Server load, and how to get most out of each CommuniGate Pro Server running in the Single-server or in the Cluster mode.