On February 29 2020, Let's Encrypt discovered a bug in how we recheck CAA records at issuance time. Details are described here. Unfortunately, this means we need to revoke the certificates that were affected by this bug. We're sending emails to everyone with an affected certificate. However, it's quite possible that your ACME client has already renewed your certificate automatically, and your new certificate doesn't have this problem. If you'd like to check, this service will help. Enter your hostname below, and it will connect to your website and check the currently available certificate, and tell you if it's one of the certificates that needs replacement or not.