Basically the missing '_' was supposed to allow DNS providers who allow programmatic DNS record creation to filter out unauthorised certificate creation. So the certificates created without it could have been unauthorized by the owner of the domain they claim to certify.
Basically the missing '_' was supposed to allow DNS providers who allow programmatic DNS record creation to filter out unauthorised certificate creation. So the certificates created without it could have been unauthorized by the owner of the domain they claim to certify.