The way DNS works, if a local resolver doesn't have the record for a domain name, then it'll ask a higher level resolver. This proposal says that .internal will

The way DNS works, if a local resolver doesn't have the record for a domain name, then it'll ask a higher level resolver. This proposal says that .internal will never be added to those higher level resolvers so if your local resolver doesn't have a record for a .internal hostname then locally that hostname doesn't exist