Rspamd

Rspamd is a fast, free and open-source spam filtering system.

Installation

To enable Rspamd add following line to your system configuration

/etc/nixos/configuration.nix

services.rspamd.enable = true;

Configuration

Whitelist domain

To whitelist a specific domain (in this example the domain example.org) which otherwise gets rejected by Rspamd for various reasons, this custom configuration override can be added:

/etc/nixos/configuration.nix

services.rspamd = {
  enable = true;
  overrides."whitelist.conf".text = ''
    whitelist_from {
      example.org = true;
    }
  '';
};

DKIM key

This module verifies the authenticity of emails through the analysis of DKIM signatures. In this example, we're configure a custom DKIM key file path suitable for the mailserver Maddy and adjust the group permissions for the Rspamd service.

/etc/nixos/configuration.nix

services.rspamd = {
  enable = true;
  locals."dkim_signing.conf".text = ''
    selector = "default";
    path = "/var/lib/maddy/dkim_keys/$domain_$selector.key";
  '';
};

systemd.services.rspamd.serviceConfig.SupplementaryGroups = [ "maddy" ];