For most of the afternoon and this morning yesterday, Mail was behaving--allowing me to read and delete apps, as well as to open links in the Edge browser. This morning, Mail hung every time I tried to reply to an email--not vanishing instantly like yesterday morning's crashes, but graying out and the window title bar indicating "(Not responding)", the OS trying to recover it, then closing Mail down. All this use has been with an Exchange ActiveSync msn/outlook.com account. Fortunately, Outlook 2013 is working fine for both that and my Exchange account from work.