In Cloudflare, I use a proxy for my domain.de to my server's ip
Use another unproxied subdomain (A) srv01.domain.de--> server ip
Use srv01.domain.de as my rDNS with my hoster
Use MX domain.de --> srv01.domain.de
Use unproxied subdomain (A) mail.domain.de --> server ip
Use srv01.domain.de as my...