Question: Do I need to purchase the Standard Edition or the Enterprise Edition of Exchange Server 2010 for my organization?
Exchange Server 2010 is available in two editions; Standard or Enterprise. The only difference between these two product editions is how many databases (of either mailbox or public folder type) it can host.
- Exchange Server 2010 Standard Edition can host up to 5 databases
- Exchange Server 2010 Enterprise Edition can host up to 100 databases
This makes selecting Exchange Server 2010 licenses fairly simple.
- Use Exchange Server 2010 Standard Edition for all Client Access, Hub Transport, Edge Transport, and Unified Messaging servers
- Use Exchange Server 2010 Standard Edition for Mailbox servers that require 5 or fewer databases
- Use Exchange Server 2010 Enterprise Edition for Mailbox servers that require more than 5 databases
For Mailbox servers that are members of a Database Availability Group each passive copy of a database counts as a database on the server. So if a Mailbox server has 4 active mailbox databases and another 4 passive copies it will need to be running the Enterprise Edition of Exchange Server 2010.
However, Exchange 2010 Enterprise Edition is not required for DAG members that host 5 or fewer active and passive databases. A common misconception is that Enterprise Edition is required for Exchange high availability. This is not true, DAG members can run either Standard or Enterprise edition (even within the same Database Availability Group).
However all DAG members must run Enterprise Edition of Windows Server 2008 or 2008 R2, which is required for the underlying Failover Cluster that the DAG utilizes.
The edition of Exchange Server 2010 is solely determined by the product key that is entered after the server is installed. When the server is running in 120 day trial mode (ie without a product key) it operates under the limits of Standard Edition. A server can be upgraded to Enterprise Edition simply by entering the new product key.
You can read more about Exchange Server 2010 licensing on the Microsoft website: