Hi, I'm the author of the blog post being promoted here.
No, this is not possible. Cloudflare Tunnel focuses mainly on HTTP traffic but also supports SSH, VNC and generic TCP only in situations where the client also uses the cloudflared client to proxy it back to their localhost. Hosting a mail server with these restrictions is not possible I'm afraid.
No, this is not possible. Cloudflare Tunnel focuses mainly on HTTP traffic but also supports SSH, VNC and generic TCP only in situations where the client also uses the cloudflared client to proxy it back to their localhost. Hosting a mail server with these restrictions is not possible I'm afraid.