I installed Windows 10 last Saturday and on Sunday I found that 4 month's e-mail had been wiped from my BT Mail in-box. Any explanation would be gratefully received. I received a load of spam on Sunday, but nothing of consequence,
What email client are you using and is it the same client you were using before the Win 10 install?
What type of Windows 10 Log on account name are you using i.e. same account name you used in your previous windows or is it a new Microsoft Win 10 account e.g. '[email protected]'?
Can you see emails that exist prior to the 4 month loss?
Have you checked your junk / spam folders to see if they have somehow been moved to there?
And instead of using the email app, if you log on to the email using a internet can you see them there? I had the same issue, and once I had seen they were still there in the internet, I used the synch to show them in the email app.