Apparently, configuration of outgoing mail is more than just installing postfix because of anti-spam measures. Consider my pet project iryska.com.ua: 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 mail-tester.com
- Google how to resolve the most critical problem
- Fix it
- Repeat until satisfied with the result
Thus, the following had to be fixed:
And there is the result now: