The email that I used is not publicly well known, so I would be surprised if this were the case.
Could this be a phishing campaign that tricks Let's Encrypt to send emails on the behalf of a threat actor? For example, the threat actor knows user@example.com owns a domain, so creates many ACME accounts with that email for domains that host malware. Then user@example.com receives an email from Let's Encrypt so is more likely to click the link to the incorrect malware domain.
I am the original owner and host of all domains and ACME accounts associated with that email.