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:
A name server requires set up with DNSSEC.
Choose a better host in case of outdated setup.
Enabling DNSSEC for mail servers is ongoing.