It appears that the NNTP server at news.digitalmars.com cannot be reached over TLS, only over plaintext. Is that correct? I tried both STARTTLS, and port 563. It would be great if the server could be reached over TLS on port 563, especially since it is underlying infrastructure for the forums.

The website on the same domain is already available over TLS, so it may be a simple matter of installing a TLS terminating proxy that uses the same certificate files.