Every time you have problems that your self hosted email is blocked by Microsoft or Google. And you have no idea why because all you get from them are template replies, and then someone comes along and asks:
"Have you set up SPF, dkim and dmarc for your domain?"
A fairy dies.
@joao +1 We get bitten by this at work occasionally. IMHO this is Google/MS mis-using the standards. SPF and DKIM are supposed to be used during the SMTP negotiation, so a legitimate sender will get the rejection via "Return-path:". Also passing one of SPF or DKIM should be enough. Google does this, but seems to use SPF/DKIM post-delivery for spam filtering and domain listing as well, and requires them both to pass. We emit no spam but still get bitten. It feels like Google is bullying us.
