> You don't have to, this is the key reason to have a DMARC monitoring service. It will tell you when there's a deliverability issue with some particular receiver.

It's been a while, but monitoring DMARC seemed pointless once you got things started. If my outbound mail fails to validate, I've asked the receivers to bounce it, and I should be able to see that on my own system.

Otherwise, I'm just getting reports about spoofed spam or people who need to adjust their mail forwarding, but I can't do anything about either.

right, if you're at a reject status DMARC monitoring is (and should be) boring.

But it provides a safe guard against accidentally broken mail flows as your email stack evolves over time which is where it pays dividends.

I would love to say that it would have alerted you ahead of time to this particular event, but given that it's the fix here you would never have seen it.