Don't get me wrong, OL 2016 worked well for me under El Capitan, however, many of the new features I don't need, i.e. Exchange features, enhanced calendar features. While lots of new features were added to OL 2016, some features were left out... notably Apple Script... essential to me, I use SpamSieve. I realize there is a work around for this, but I would rather not be forced into work arounds. Additionally, I prefer the OL 2011 interface over the OL 2016. The remainder of the suite works exceptionally well and I use most of it every day.