Rspamd Spam filter

Introduction

Rspamd is an open source email spam filtering tool that can be integrated with KumoMTA

Instructions

First things

Spam filtering engines can be complex and require an understanding or patern matching and email handling rule sets. Please read through the quickstart documentation FIRST before proceeding: https://docs.rspamd.com/tutorials/quickstart/

Get KumoMTA

Install KumoMTA as per the installation instructions here.

Before finishing this step, you should ensure that you have correctly set up DNS with a resolving sending domain, MX, PTR, SPF, DKIM, etc.

Ensure that you can inject and deliver mail through KumoMTA.

Add the following to your init.lua config, in the top part of the config, before the init section, place this variable declaration:

local RSPAMD_URL = 'http://localhost:11333/checkv2'

Then in the smtp_server_message_received event add code to pass the message to rspamd for evaluation:

kumo.on('smtp_server_message_received', function(msg, conn_meta)
  local request = kumo.http.build_client({}):post(RSPAMD_URL)
  request:body(msg:get_data())
  local response = request:send()
  if response:status_code() == 200 then
    local data = kumo.serde.json_parse(response:text())
    if data['score'] >= 15 then -- rspamd recommends rejecting the message
      kumo.reject(550, 'We do not send spam')
    end
  end
  -- the rest of your handler
end)

Note that you can modify the score threshold and reject message as needed.

Get Rspamd

Read and follow the first 3 (THREE) steps in this guide: https://docs.rspamd.com/tutorials/quickstart/

STOP when you hit step 4. Do NOT install Postfix.

Restart the rspamd process with sudo systemctl restart rspamd

Continue the install and test process starting at step 5 (five) here: https://docs.rspamd.com/tutorials/quickstart/

Your rspamd configuration should now test every mesage injected to KumoMTA.