Setting that up is immensely difficult, and managing it will probably slow down your DNS queries, but if you are a veteran While using the Linux command-line, take a look at Cloudflare's instructions for DNS in excess of HTTPS and DNS over TLS. To help with Configuration Supervisor client performance https://remingtonrymat.uzblog.net/the-smart-trick-of-iredmail-installation-that-no-one-is-discussing-40406166