TNEF is a container/encapsulation format rather than a markup language. It can contain HTML as well as RTF and plain text.
Granted HTML rendering of email is full of quirks in Outlook
Granted HTML rendering of email is full of quirks in Outlook
We already have the 365 Web version for that.
Yet another example of Microsoft's failure to hire employees with native Windows development skills, now with the old guard that grew up with Win32 are reaching retirement age.