wikipedia.org:
https://en.wikipedia.org/wiki/Domain_Name_System_Security_Extensions

testing tool:
https://dnssec-analyzer.verisignlabs.com/

Error example, checking on internet.nl:
Too bad! Your domain is not signed with a valid signature (DNSSEC). Therefore visitors with enabled domain signature validation, are not protected against manipulated translation from your domain into rogue internet addresses. You should ask your name server operator (often your registrar and/or hosting provider) to enable DNSSEC.

Check DNSSEC properly:
DNSSEC requires an identification code on the name server.
Choose a better domain provider in case of outdated setup.
Both Google and Microsoft are trying to get along with enabling DNSSEC for their mail servers.