Exchange Server 2013 Enterprise Device CAL
IMPORTANT NOTE: You must buy at least 5 CALS. New orders must also purchase a server license along with at least 5 Standard CALs.
The Enterprise CAL is sold as an Add-on to the Standard CAL. To enable Enterprise CAL features the user must be licensed with one Standard CAL plus one Enterprise CAL. The Enterprise CAL is designed to allow organizations to reduce the costs and complexity of meeting compliance requirements with new integrated archiving functionality and information protection capabilities while also helping you cut costs by replacing legacy voice mail systems with Unified Messaging.
A Device CAL permits one device (used by any user) to access or use Exchange Server. Device CALs are likely to be more cost-effective than User CALs if there are multiple users per device (for example a call center or an airport kiosk). A minimum of 5 CALs and a server license is required.