I have a root domain that is set up to use my main mail server which resolves properly & able to send/receive mail.
I’ve added a subdomain for a site that is hosted on a different server, using it’s own mail server. I’ve added all the required MX/TXT/PTR entries & ran some tests. The new subdomain IP address is resolving to a Cloudflare public IP address instead of the actual hostname of the server, resulting in only being able to receive mail & not send.
I have tried with orange & grey cloud for the domain & does not make a difference, keeps resolving to the Cloudflare IP.