Right. And if you mandate dkim, as seems to be the case with servers that demand dmarc, what's the issue? You reject the emails where dkim isn't set.
Or do you think it's critical to support mail that doesn't have dkim?
Or do you think it's critical to support mail that doesn't have dkim?
Setting a DMARC policy that allows unsigned emails is easier than configuring DMARC signing including key management. It's just adding a DNS record. Although large senders should of course do DKIM and it's not that hard either
But I'm not arguing with you about whatever Outlook did.