Microsoft Exchange Server is one of the common email servers used across organizations. As a result of recent enhancements in Microsoft Exchange Server, you can securely connect to it over the Internet. Depending on the available bandwidth, you might experience latency in the email delivered to the Outlook client. In addition to the MAPI protocol, the CloudBridge appliance supports Remote Procedure Call over HTTPS (RPC over HTTPS) to optimize Microsoft Exchange traffic. This feature is also known as Outlook Anywhere.
RPC over HTTPS is not a new protocol, but starting with Microsoft Exchange 2013, it replaces MAPI as the default protocol. The main advantage of RPC over HTTPS is that it enables clients to securely connect to the mail server over the Internet.
When you use RPC over HTTPS, the Microsoft Exchange server must use a digital certificate and private key to authenticate itself to the Outlook client. The communication between the client and server uses HTTPS as a transport protocol.
Of these, all versions except Microsoft Exchanges Server 2013 support MAPI (over TCP) as well as RPC over HTTPS. However, Microsoft Exchange Server 2013 forces connections to use RPC over HTTPS, regardless of the Microsoft Outlook version you use, to connect to the Exchange server.