Solution for unable resolving an A record with an intranet address when using pfSense

If you are having trouble resolving a domain name with an A record as an intranet address when using pfSense, add the following field to the Custom options of your DNS Resolver settings.

server:
private-domain: "example.com"

Reference:
https://docs.netgate.com/pfsense/en/latest/services/dns/resolver.html#dns-resolver-and-dns-rebinding-protection