There is a clients domain, let's name it www.client-xyz.example, which was hosted with a web space package on a web host. I created a new homepage which is located on my server and I pointed the A-Record to my servers IP so that the visitors reach my server over the IP. That's working fine and as excepted!
The problem is that the mail service, which is controlled by cPanel on the old host wont work now! It seems like all mail connections reach the wrong server. If I send a email to one of the email addresses it gets rejected by my server instead of using the SMTP server from the old host.
Which DNS Record can I use to adjust it?
Arecord rather than aCNAMErecord? Using aCNAMErecord at the domain apex (no subdomain) isn't allowed. If you try to do so, one symptom is that your email will break like this.