The Spam Experts email filtering solution is always installed on at least 2 servers. All filtering nodes are fully synchronized and controlled from the API/web interface.
There are different services run by machines within the cluster, by default the primary server includes all services:
- API/Web interface
- IMAP quarantine
- Archive storage
Extra machines added only perform the role of filtering node and do not contain the other mentioned services. These extra machines are so-called "secondary servers" and are synchronized in real time with the data from the primary machine. The physical location of the secondary server can be anywhere, and does not depend on the primary location. If the primary would be unreachable or down, the "secondary machines" will keep processing the emails.
The specific primary functionality is only available when the primary is reachable, as messages quarantined or logged are queued on the filtering secondaries whilst the primary server is unreachable and will automatically synchronize again as soon as it is back online. The logging, quarantine and archive storage can be hosted on the primary (default) or be moved to any of the secondary servers.
Each filtering node can handle both primary and fallback email. The distinction between primary email (lowest MX priority) and fallback email (highest MX priority) is made automatically based on the IP address used. Each server can be used only as primary server, only as fallback server, or (with 2 IPs) both as primary server and fallback server at the same time. This last setup ensures optimal use of the hardware resources available. For more information see Local Cloud MX Records.
IP address change
If the IP address of a server changes, this will break the synchronization and authorization of the system as part of the cluster. Five days prior to changing your IP address please inform us to schedule a free IP change.
It's currently not possible to change the hostnames of the servers. This will require a reinstallation for which we charge a fee.
Cluster size and distribution
We recommend a minimum of 2 servers, and 50% of the servers to be located in another network/datacenter (for redundancy).
Please note that although it's technically possible to run on a single machine, we strongly recommend against that as an outage would mean the entire mailflow would stop. As our backups are between the Spam Experts systems, there is no backup in a single-machine setup and as the traffic cannot be distributed we only provide limited monitoring/support for such setups.