6.1.2.5 Misusing Configuration Info: RFC-1035 Section 6.1.2

Recursive name servers and full-service resolvers generally have some configuration information containing hints about the location of root or local name servers. An implementation MUST NOT include any of these hints in a response.

DISCUSSION:

Many implementors have found it convenient to store these hints as if they were cached data, but some neglected to ensure that this "cached data" was not included in responses. This has caused serious problems in the Internet when the hints were obsolete or incorrect.