The cluster back-end systems are the actual information center for the entire setup. The system or systems that make up the back-end area of any cluster require access to storage resources. Thus, the AXIGEN services that run on these systems are very similar in configuration to the services that run on any stand-alone AXIGEN server.

The back-end services used by the cluster nodes are:

SMTP Services will provide functionality for the incoming and outgoing mail received by the accounts stored on the cluster node. The SMTP incoming service will accept connections from the SMTP proxies on the front-ends.
IMAP and POP3 Services will accept routed connections from the respective proxy services. They will retrieve the information from the storage and pass it to the proxies to be displayed in the mail client.
WebMail Service will provide the information required by the WebMail proxies to render the pages requested by the client. It will not be accessible directly, only through routed connections from the proxies.
Other Services include other modules supported by the server that are independent on the cluster setup. These include the FTP Backup service, the CLI, the WebAdmin interface, RPOP etc.

These systems have domains and accounts set up locally and take care of the imposed restrictions regarding disk space usage and quota management. All details concerning the actual user account settings must be defined and configured on the back-end systems, through any of the administration interfaces.

All services that make use of an authentication mechanism in a cluster, using LDAP authentication, should also use this type of authentication in the back-end section. This is recommended because using the same resource to authenticate sessions provides increased integrity to the whole clustering system. Because LDAP authentication can be used by both routing and non-routing services, this approach should make sense in most cluster setups.

NOTE: In the back-end, no routing is performed and consequently, no proxy services should be running. As such, while an LDAP connector can be defined to enable directory authentication, this connector should not be used to map any connections.

WARNING: Setting up a routing SMTP service in the back-end will cause looping messages that will be discarded.

Individual service configuration, except the authentication method, should be fairly straight-forward and easy to perform, as the services themselves are not different in any way from the services used by any other AXIGEN server.