But can you sync calendars and contacts? CalDAV and CardDAV are the standards talked about in the article. They’re supported internally, but you seem to have no way to add the URLs if it’s anything other than the mentioned providers.
The article is about the CalDAV and CardDAV protocols which is the IMAP equivalent for syncing your calendars and contacts.
So the article incorrectly titled as it uses word "email" while W10 does support arbitrary POP/IMAP/SMTP mail systems.