Error while install in both 22.04 and 24.04

Yes. But you can't use Let's Encrypt when you turn on proxying at CloudFlare, as CloudFlare then blocks the verification request from Let #s Encrypt, so the cert will not validate. But you can create a self-signed certificate in ISPConfig for that site, the user will see the CloudFlare cert only anyway.

 

That's not ISPConfig specific. When you use CloudFlare, ensure not to create any DNS records in ISPConfig as CloudFlkare is your DNS system and not ISPConfig. An MX record is a record that must point to an A-record, and that A-record must point to the IP of your email server. The MX record itself must be for the domain for which you want to receive the email.

If you are not using CloudFlare, then take a look here: https://www.howtoforge.com/tutorial/setting-up-your-own-name-service-with-ispconfig/

 

You mean in ISPConfig? You should not choose an IP there, you should use the default which is "*". Please try to read the documentation first before asking as we can not explain every user one after another every bit on how web hosting works individually: https://www.howtoforge.com/ispconfig-website/