Like, I have a ton of problems with #DMARC, but the one thing that it is absolutely, positively good for is putting DMARC records on domains that legitimate email never originates from to tell receiving servers, "Yo, don't trust anything that comes from this domain, it's lying."
Heck, I think there's even a federal government binding directive requiring DMARC on all government domains.
Oh, wait, here it is. It came from… CISA. Because of course it did. #irony
https://www.cisa.gov/news-events/directives/bod-18-01-enhance-email-and-web-security