Using the KumoProxy SOCKS5 proxy utility
KumoMTA comes with its own SOCKS5 proxy server to assist with deployment of cluster environments.
The binary is located at /opt/kumomta/sbin/proxy-server and can be operated independently from KumoMTA.
To run the proxy on a dedicated server with public-facing IPs, install the KumoMTA package on that server; you do not need to configure or start KumoMTA itself. To execute the proxy, use the command /opt/kumomta/sbin/proxy-server --listen <IP:Port>
Ensure that you have configured sysctl to allow for enough file handles, ip forwarding and other important factors.
Usage documentation is at /opt/kumomta/sbin/proxy-server --help
Configuring KumoProxy to survive a restart
KumoProxy can be configured as a systemd service
Note that this has only been tested for Ubuntu 24. Your OS may require slightly different configuration.
You will need sudo access to perform these changes. Start by creating a service file.
sudo vi /etc/systemd/system/kumoproxy.service
Populate it with:
[Unit]
Description=KumoMTA SOCKS5 Proxy service
After=syslog.target network.target
[Service]
Type=simple
Restart=always
EnvironmentFile=-/opt/kumomta/etc/kumoproxy.env
ExecStart=/opt/kumomta/sbin/proxy-server --listen ${PROXY_IP}:${PROXY_PORT}
TimeoutStopSec=10
[Install]
WantedBy=multi-user.target
Next, create an environment file where you can add your system variables.
sudo vi /opt/kumomta/etc/kumoproxy.env
Populate with your IP and Port
For example:
Reload the services:
sudo systemctl daemon-reload
Now you can start, test status and enable like any other service. Do these manually once to ensure the service starts. After it is enabled it will restart automatically on reboot.