Thank you D4niel for the reply,
I would like to share what I did, as this may also help others with their set up.
I am using GoDaddy to as my URL host and CloudFanatic as my VPS (Virtual Private Server) provider.
To set rdns in your dashboard hover over Services -> click Manage DNS -> click the RDNS tab -> click the Add PTR button and proceed from there.
In your VPS (in my example CloudFanatic), log in and hover over services and then click “Manage DNS”.
![](https://community.mailcow.email/assets/files/2023-08-24/1692837953-774874-screenshot-from-2023-08-24-07-40-19.png)
Click on the rDNS tab.
![](https://community.mailcow.email/assets/files/2023-08-24/1692837983-353942-screenshot-from-2023-08-24-07-40-38.png)
Enter the rDNS information, which should be the FQDN (your subdomain.URL.com, for example).
![](https://community.mailcow.email/assets/files/2023-08-24/1692838230-672672-screenshot-from-2023-08-24-07-49-37.png)