Not sure what's going on, but I got a new galaxy S5 from At&t, and the authentication fails when trying to setup my exchange account.
A little background. I switched from Verizon to At&t " Long story". Anyway I actually Got my Boss a new Galaxy S5 as well except his phone is with Verizon. I had no problem setting up his exchange account on the exact same phone. The only difference is that mine is with AT&T.