DMARC Reporting

DMARC Reporting done via Rspamd DMARC Module.

Rspamd documentation can be found here: https://rspamd.com/doc/modules/dmarc.html

Important:

1. Change example.com, mail.example.com and Example to reflect your setup

2. DMARC reporting requires additional attention, especially over the first few days

3. All receiving domains hosted on mailcow send from one reporting domain. It is recommended to use the parent domain of your MAILCOW_HOSTNAME:

   • If your MAILCOW_HOSTNAME is mail.example.com change the following config to domain = "example.com";
   • Set email equally, e.g. email = "noreply-dmarc@example.com";

4. It is optional but recommended to create an email user noreply-dmarc in mailcow to handle bounces.

Enable DMARC reporting

Create the file data/conf/rspamd/local.d/dmarc.conf and set the following content:

reporting {
    enabled = true;
    email = 'noreply-dmarc@example.com';
    domain = 'example.com';
    org_name = 'Example';
    helo = 'rspamd';
    smtp = 'postfix';
    smtp_port = 25;
    from_name = 'Example DMARC Report';
    msgid_from = 'rspamd.mail.example.com';
    max_entries = 2k;
    keys_expire = 2d;
}

Create or modify docker-compose.override.yml in the mailcow-dockerized base directory:

version: '2.1'

services:
  rspamd-mailcow:
    environment:
      - MASTER=${MASTER:-y}
    labels:
      ofelia.enabled: "true"
      ofelia.job-exec.rspamd_dmarc_reporting.schedule: "@every 24h"
      ofelia.job-exec.rspamd_dmarc_reporting.command: "/bin/bash -c \"[[ $${MASTER} == y ]] && /usr/bin/rspamadm dmarc_report > /var/lib/rspamd/dmarc_reports_last_log 2>&1 || exit 0\""
  ofelia-mailcow:
    depends_on:
      - rspamd-mailcow

Run docker compose up -d

Send a copy reports to yourself

To receive a hidden copy of reports generated by Rspamd you can set a bcc_addrs list in the reporting config section of data/conf/rspamd/local.d/dmarc.conf:

reporting {
    enabled = true;
    email = 'noreply-dmarc@example.com';
    bcc_addrs = ["noreply-dmarc@example.com","parsedmarc@example.com"];
[...]

Rspamd will load changes in real time, so you won't need to restart the container at this point.

This can be useful if you...

• ...want to check that your DMARC reports are sent correctly and authenticated.
• ...want to analyze your own reports to get statistics, i.e. to use with ParseDMARC or other analytic systems.

Troubleshooting

Check when the report schedule last ran:

docker compose exec rspamd-mailcow date -r /var/lib/rspamd/dmarc_reports_last_log

See the latest report output:

docker compose exec rspamd-mailcow cat /var/lib/rspamd/dmarc_reports_last_log

Manually trigger a DMARC report:

docker compose exec rspamd-mailcow rspamadm dmarc_report

Validate that Rspamd has recorded data in Redis: Change 20220428 to date which you interested in.

docker compose exec redis-mailcow redis-cli SMEMBERS "dmarc_idx;20220428"

Take one of the lines from output you interested in and request it, f.e.:

docker compose exec redis-mailcow redis-cli ZRANGE "dmarc_rpt;microsoft.com;mailto:d@rua.agari.com;20220428" 0 49

Change DMARC reporting frequency

In the example above reports are sent once every 24 hours.

The Ofelia schedule has the same implementation as cron in Go, supported syntax described at cron Documentation

To change schedule:

1. Edit docker-compose.override.yml and a djust ofelia.job-exec.rspamd_dmarc_reporting.schedule: "@every 24h" to a desired value, for example to "@midnight"

2. Run docker compose up -d

3. Run docker compose restart ofelia-mailcow

Disable DMARC Reporting

To disable reporting:

1. Set enabled to false in data/conf/rspamd/local.d/dmarc.conf

2. Revert changes done in docker-compose.override.yml to rspamd-mailcow and ofelia-mailcow

3. Run docker compose up -d

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Last update: 2022-10-23 16:41:00