As briefly touched upon during Chapter 1, Planning an Exchange Server 2013 Infrastructure, Exchange 2013 stepped away from familiar RPC-over-TCP connections and now only uses RPC-over-HTTP connections for primary client connectivity. This means that now both internal and external clients connect to Exchange using Outlook anywhere.

By default internal connections are not secured (plain HTTP). Usually though, companies want to secure that traffic using Secure Sockets Layer (SSL).

SSL has two main functions:

For both of these tasks, SSL relies on certificates. It's not necessary to know all the details of how certificates work. However, it's important to have at least a basic understanding of the implications of working with certificates, especially given the criticality of properly configured certificates in Exchange Server 2013.