I have run Windows 8 on my Intel PC since it came out. I did take the Windows 8.1 upgrade. I have experienced issues with some folders not syncing over the last six months or so, but now the native Mail app stopped working entirely.
I can invoke the app but no new mail loads. I can press the Sync button, no joy. I can start a New Email, compose and send, but it never arrives.
Mail comes in fine for the same Windows account on my laptop. Issue is only on my desktop PC.