Clustering

KumoMTA is designed to be used in high-volume sending environments where cluster capabilities are essential to effective and manageable scaling.

To address these needs, KumoMTA has several features and integrations designed around cluster management.

Implementation Approach

The KumoMTA team works from a philosophy of "don't re-invent the wheel". To the degree possible KumoMTA is designed to work with existing solutions rather than implement our own version of existing tools.

For example: KumoMTA does not provide a configuration distribution or versioning tool because there are numerous existing options including Git, Puppet, Chef, K8s, etc.

Vertical vs Horizontal Scaling

While many existing users coming from commercial MTAs with per-node licensing tend toward vertical scaling, KumoMTA can be either vertically or horizontally scaled.

Vertical scaling with high-performance hardware can see over ten million messages per hour on a single node, where horizontal scaling environments tend to aim for between two to four million messages per hour per node. Those leveraging orchestration solutions such as Kubernetes will likely prefer a horizontal scaling architecture.

Shared Vs. Node-Specific Configuration

While it is possible to configure KumoMTA nodes in a cluster with distinct configurations on a per-node basis, the traffic shaping approach used in KumoMTA is most effective when all nodes share the same IP configuration using proxies.

In this approach the nodes share a common configuration (implemented using the preferred method of the user) with the Egress_Source configured to use a proxy for sending. Alternatively Reverse NAT or port forwarding could also be used.

KumoMTA supports both HAPROXY and SOCKS5, see the Proxy page for information on using KumoMTA with outbound proxies.

KumoMTA includes a SOCKS5 proxy implementation, see the KumoProxy page for more information.

Managing Shared Secrets

One of the most straightforward ways to manage secrets such as DKIM keys and authentication credentials is using a Vault.

For more information on using Vault for shared secrets see our Storing Secrets in Hashicorp Vault page.