The year is 2016 and Apple Mail still sucks.
Apple, why even bother with Apple Mail? You obviously have no passion for it. It is gutter CRAP! REMOVE IT!
I went to a Mac from MS based boxes back in 2011 and was surprised at how bad the Apple Mail app was back then. It is now 2016 and I dare say Apple Mail is worse now than I have ever seen it before.
Yeah, yeah, yeah, I have read and tried all of the fixes and work-arounds; it is still unstable garbage; I have better things to do than troubleshoot software. I have moved most everything back to Outlook for Mac 2011.