If you store your emails in a hosting provider then the hosting provider can read your emails. If you store your emails at your server at home then police can break your door plug in to your server and read your emails. Even if the disk is encripted they can read the encription key from the memory. Now I trust more Google than Microsoft, if you are non USA citizen of course. And I trust a foregn authority more than a local. This can change in for your case.