I've upgraded my wife's laptop to W10. (She hated/despised W8, W8.1, until I installed the Start8 shell.) Whereas W10 is a great improvement, the bundled email software is not.
W10's mail program does not allow new folders to be created (you can add pre-existing ones, but you cannot make your own); it does not allow you to look at all unread emails (you've got to go into each account); the upgrade process wiped out all her contacts (I'm hoping they still exist somewhere on her hard-drive).
How do I reinstall Windows Live Mail?