We learnt that “Authoritative DNS lookup problems for some Free plan zones” happened Jun 21, 2021 from Cloudflare System Status. It identified on UTC 13:54 and resolved on UTC 21:25. We know Cloudflare need time to fix and keep monitoring. During that time, several customers complain through Telephone that they cannot send email to us and receive “451 4.4.0 DNS query failed” error message. Is it possible to notify user or register like us that you were identifying, investigating, fixing, … Otherwise, we need to try, find possible cause, and comfort customer.
Cloudflare seems to have turned off the statuspage feature that allows you to sign up for notifications, however you can still subscribe to the RSS feed with your favorite RSS/atom reader or mobile app. https://www.cloudflarestatus.com/history.atom