I just finished adding a feature to https://port87.com/ that lets you turn message authentication requirements completely off for a label.

I did this specifically because all of my email accounts will reject email from my home server’s disk monitoring software because it’s not set up to send email “correctly” (no DKIM or SPF, no MX record on its return path).

I figured since I made my own email service, and you can have setting per address (each label has its own address), it would be easy to add this feature. It was not that easy. One of the plugins in the server I use (Haraka) would reject email if it failed its check. I contributed a PR to Haraka to make the failure on that check optional. Yay open source!