Reading Time: 3 minutes There are several ways how you can protect and limit access to Exchange Online. Conditional Access, Client Access Rules, the older ActiveSync Device rules and, the topic of this post, Authentication Policies. These policies are available in Exchange Online and Exchange Server 2019 since CU2. This article will show you how to implement this. Why use Authentication Policies? Authentication Policies only do one thing: enabling or disabling legacy or basic authentication (I use both terms) on protocols used by Exchange