Setting that up is immensely intricate, and running it will most likely slow down your DNS queries, but should you be a veteran with the Linux command-line, take a look at Cloudflare's Guidance for DNS about HTTPS and DNS over TLS. The padlock icon and HTTPS in the URL https://cloudflarefreessl18517.dbblog.net/58739663/getting-my-linux-postfix-mail-server-setup-to-work