From what I have understood of our interaction thus far, I will tell you what I would have done on a fresh install of Virtualmin to get the result you want:
- Configure jordijuan.com, www.jordijuan.com vps.jordijuan.com ns1.jordijuan.com, ns2.jordijuan.com, mail.jordijuan.com, diania.tv, www.diana.tv and mail.diana.tv to point to the IP addresses (IPv4 and IPv6) of the VPS
- Install Virtualmin on VPS
- Set hostname to vps.jordijuan.com and set name servers to ns1.jordijuan.com and ns2.jordijuan.com
After installation is complete, reboot server, visit vps.jordijuan.com:10000, login as root and run Virtualmin >> System Settings >> Re-Check Configuration. Let’s assume everything is okay at this point. Then:
- Create a virtual server vps.jordijuan.com, in Enabled Features, disable Mail for domain checkbox. After virtual server is created, apply for Lets Encrypt certificates, apply these to Webmin, Virtualmin, Postfix and Dovecot
- Create a virtual server jordijuan.com
5a) Edit users, create a user (or a few)
- Create a virtual server diania.tv
6a) Edit users, create a user (or a few)
Do a quick check, if you wish, to see if www.jordijuan.com and www.diana.tv are showing a 404 or similar error, as we would expect at this point. Regardless, let us proceed with getting mail working.
Now setup your email client with incoming / outgoing server set to vps.jordijuan.com and username + password as you have specified in 5a and 6a. To test if email is working, send and receive a few messages. These will likely be flagged as spam, but they will leave your server and be delivered to the destination mailbox. So far so good.
To avoid getting email from your server flagged as spam, you will have to enable DKIM in Virtualmin and apply the keys to the DNS records of jordijuan.com and diana.tv if you are using a third party DNS service for these domains. Finally you will have to set up RDNS for the IP address of the VPS to be vps.jordijuan.com. Your email should now land in the inbox rather than get flagged as spam.
Hope this is all clear. If you run into trouble at any point, let us know at which step and we can try and help you with that.