Troubleshooting 4 different types of Microsoft DKIM rejections

If your attempts to send email to Microsoft-hosted inboxes are bouncing back intermittently with authentication-related rejections; specifically highlighting that DKIM is failing, when you know you’ve got DKIM authentication correctly implemented: what do you do now?The actual SMTP rejection looks something like this: “550,5.7.515,Access denied, sending domain example.com doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , DMARC= Pass”Almost hidden in the massive SMTP response, near the end, is that “Dkim= Fail.” But you didn't misconfigure DKIM, so you're confused. And rightly so; it's a tricky issue with multiple possible root causes.Here, in my latest Valimail “Ask Al” video, I walk you through four things I would look for when trying to troubleshoot this issue: DNS…