I've never been a fan of stock email going back to the S5. I'm also not a fan of the Gmail app either. I used CloudMagic for quite some time until they changed to Newton. Then onto TypeApp, which was identical to CM. Then I stumbled across Samsung's Focus app, which despite a few flaws, I still love and have been using for probably 6 months.
It's kind of an all-in-one digital day planner that functions more like Outlook desktop for Windows machines. Within 1 app I can view emails, contacts, calendar, notes, etc. Sammy still needs to smooth out some rough edges and add some additional features, but I'm hopeful that they'll stick with it as it could easily eliminate the need for several apps.