IMPORTANT NOTE: New orders must also purchase a minimum of 5 CALs
Exchange Server 2010 Standard can help you achieve better business outcomes while controlling the costs of deployment administration and compliance. Exchange delivers the widest range of deployment options integrated information leakage protection and advanced compliance capabilities that combine to form the best messaging and collaboration solution available. There is a reason Exchange Server is the industry's leading server for e-mail calendaring and unified messaging. The Standard Edition is limited to 5 databases per server.
Microsoft Open Licensing allows the ability to purchase under the same authorization number for two years. Open Business offers volume pricing with only a five minimum license requirement.