Since David Moore has also posted elsewhere about this he is using the new Win10 mail app that ships with every Win10 machine and shows up on the start menu out of the box.
It's got little in common with earlier e-mail clients other than the fact that it is used to read mail.
I'm still not able to get message text read using NVDA and the Win10 mail app, but I'm presuming that this is operator error of some sort.
Never underestimate the difficulty of changing false beliefs by facts.
~ Henry Rosovsky