I found this online - The Android 5.1.1 Lollipop update for the Nexus 6 is quite minor, bringing various stability improvements and a new protocol that disables Smart Lock feature on the device when the Exchange ActiveSync (EAS) password policy is enforced.
EAS is a Microsoft protocol, which allows users to save Windows email and contacts across various devices. This protocol does not work in accordance with Google’s Smart Lock feature, which allows a Nexus 6 handset to unlock when paired to a designated wearable, bluetooth device, location or the sound of a user’s voice.