Microsoft have announced that the new high availability feature of Exchange 2010, namely, Database Availability Group, or DAG will be available in Exchange Standard edition. This is yet another great way they are helping make high availability affordable and appealing to smaller customers.

It is also worth mentioning though that since a DAG makes use of Windows Failover Clustering (WFC) included with Windows Server 2008 Enterprise edition, this Windows Server edition is still required.

For more info see this UC Blog post

For more info on DAG’s, click here