Most likely it's that your email is being used. We've seen some shared web hosts (see threads 1, 2, 3, 4) that didn't realize (or didn't implement correctly) that the email address is supposed to be the subscriber that can do something about renewals, and end up having all their domains be on an ACME account with an email address that just happens to be for one of their domains.)
Do you have any domains with a Let's Encrypt certificate? If so, is it something integrated with your hoster's control panel or do you run your own client like Certbot on a virtual server?