I've recently been trying to get a better handle on how email works and how it's secured. If you want to do the same. Go try out the exercises at https://www.learndmarc.com.

It's a great resource for visualizing how DMARC works in conjuction with Sender Policy Framework (SPF) and Domain Keys Identified mail (DKIM) to secure email and catch spam and phishing attempts.

There's even a quiz you can try to see how well you can analyze email traffic and determine the DMARC results.