Well, I use Webmin since 1978 or so, but I am just a user, so I put myself a beginner here.
I did move one website from CentOS (with Virtualmin) to a Debian10 server (no Virtualmin) - but I like to keep the old mail server on CentOS.
I use Cloudflare too. For SSL I use Letsencrypt.
Website runs fine. But email makes problems.
In cloudflare I set the A records for the domain to 188.8.131.52
Then I did an A record for MX to 184.108.40.206
It looks like the system always tries the 222 IP and mail never gets lost somewhere.
Is there any setting I can use to keep the email server on the old server? Or any workaround to make it work?
New server is typical naked nginx stack