By adding a _dmarc record to your DNS you can
receive deliverability reports on your email
Outlook.com and Google, and possibly other email providers, email a
daily report to the address in the rua field of the _dmarc record.
The capture_dmarc script is designed to be the recipient of such reports.
It takes them on standard input, decodes the MIMEtext in the email, extracts
the actual report (some providers just provide a gzipped XML file, others
encapsulate it in a ZIP file), and dumps it in a file.
Use by adding an alias in /etc/aliases like:
dmarc: |/usr/bin/python3 /usr/local/sbin/capture_dmarc.py
or similar; or you can use a procmail recipe.
The serve_dmarc script sets up a simple webserver on port 5002 using
Flask, and serves the reports. It has no security; but provides a
simple visualisation of the reports so far.
You probably need a cron job to clean up old reports too.
Suggest something like:
10 12 * * * Debian-exim find /var/cache/dmarc -name '*xml' -mtime +60 -print0 | xargs -0 rm -f
in /etc/cron.d/dmarc to remove all reports over 60 days old. (Use
the user who creates the files, not necessarily Debian-exim) in
/etc/cron.d/dmarc to remove all reports over 60 days old.