Glossary
What is SERVFAIL?
The DNS server could not complete the query. DNSSEC or authoritative server problems may be the cause.
SERVFAIL means the resolver could not complete the query successfully. Possible causes include reaching authoritative servers, server configuration or DNSSEC validation. Compare the same name and record type using another resolver, and give your DNS provider the query name and time when reporting the problem.
Example
If a DNSSEC key changes but the parent zone still has the old DS information, a validating resolver may return SERVFAIL. This is only one possible cause.
Common issue
SERVFAIL alone does not show that a domain is unregistered or prove a DNSSEC fault. Investigate the configuration before deleting records or turning off security validation.