DNS/RFC/1537について、ここに記述してください。
Common DNS Data File Configuration Errors October 1993
https://tools.ietf.org/rfc/rfc1537.txt
7. Wildcard MX records
- Wildcard MX records should be avoided where possible. They often cause confusion and errors: especially beginning nameserver managers tend to overlook the fact that a host/domain listed with ANY type of record in a zone file is NOT covered by an overall wildcard MX record in that zone;
../1535 A Security Problem and Proposed Correction With Widely Deployed DNS Software
../1536 Common DNS Implementation Errors and Suggested Fixes