On my new desktop everything works fine except Windows 10 Mail. It won't sync., refuses to recognise my password and other info, although that works perfectly well with 2 laptops we have which operate on Windows 10 too. The same password, etc., also work on a 10yr old XP.
If you have two other PC using the same Window s10 mail app, try transfering the info from a working PC to this problem PC. While I have not done this, they indicate there is a free app made to do things like this as part of Windows. Look aver this article to see if any of the apps will fill the need:
Ihave tried to transfer informations, ect... from the working computers to the new one, but after about an hour of going around in circle and getting nowhere and eventually losing Windows mail on all our other three computers, I gave up in despair on Microsoft Windows 10 mail. I contacted our ISP server i.e the Postoffice and they issued us with a new password. I can now get our mail through mypostoffice.co.uk on all our four computers. So thanks to our ISP and no thanks at all to Windows 10 unhelpfull approach. Many thanks to the forum for having woken me up.