Apparently, configuration of outgoing mail is more than just installing postfix because of anti-spam measures. Consider my pet project it did send emails as required, but I suspect most of them ended up in Spam folders of the recipients.

The solution wasn’t straight forward, but iterative:

  • Get the score and recommendations from
  • Google how to resolve the most critical problem
  • Fix it
  • Repeat until satisfied with the result

Thus, the following had to be fixed:

  • SPF records in DNS
  • MX records in DNS
  • DKIM
  • Postfix configuration

And there is the result now:

Mail test