rspamd/test/functional/configs/rbl.conf

rbl {
  rbls {
    fake {
      from = true;
      ipv4 = true;
      ipv6 = true;
      rbl = "fake.rbl";
      symbol = "FAKE_RBL_UNKNOWN";
      unknown = true;
      returncodes = {
        "FAKE_RBL_CODE_2" = "127.0.0.2";
        "FAKE_RBL_CODE_3" = "127.0.0.3";
      }
    }
  }
}