are you using your Hotmail email account with the Windows 10 'Mail and Calendar.app',
another Windows 10 'Mail.app' from the store or 'Windows Essentials 2012',
I use 'Windows Live Essentials 2012' & have the 'Mail shortcut' pinned to my Start Program,
been running it on this PC since July 29th & on my other PC since the Preview Evaluation started,
with no problems