On my NixOS installation I have Vixie cron installed, that runs regular jobs. The output for the scripts that are run is sent by e-mail using a ssmtp on the same host, that forwards the mails to my standard mail server (Postfix with rspamd).
My problem now is that most of these mails are stored in my Spam folder by the mail server. I checked the classification that is done by the spam filter and saw that one big 'problem' is that the messages sent by cron don't include a Message-ID header.
I searched for options to let crond generate message-ids or ssmtp to inject message-ids if they are not present yet (like other MSA can do). For neither of these I found a way to implement that.
What could I do to handle that better and to make sure these administrative mails are not classified as Spam?
