Windows Server 2019 domain Controller PKI certificates must be issued by the DoD PKI or an approved External Certificate Authority (ECA).

A PKI implementation depends on the practices established by the Certificate Authority (CA) to ensure the implementation is secure. Without proper practices, the certificates issued by a CA have limited value in authentication functions. The use of multiple CAs from separate PKI implementations results in interoperability issues. If servers and clients do not have a common set of root CA certificates, they are not able to authenticate each other.