pfSense not forwarding DNS to concerned VPS

Solution 1:

This issue is very well documented in Pfsense with workaround: DNS Rebinding Protections

The DNS forwarder (dnsmasq) uses the option --stop-dns-rebind by default, which rejects and logs addresses from upstream nameservers which are in the private IP ranges. In the most common usage, this is filtering DNS responses received from the Internet to prevent DNS rebinding attacks. Internet DNS responses should never come back with a private IP, hence it's safest to block this.

There are some cases when public DNS servers have private IP address replies by default, though it is not recommended. In those cases, DNS rebinding can be disabled or an override may be placed in the DNS Forwarder Advanced Settings box as follows:

rebind-domain-ok=/mydomain.com/

Note this is automatically overridden for domains in the DNS forwarder's domain override list, as the most common usage of that functionality is to resolve internal DNS hostnames.