HP Storage Mirroring V5 Software - Manual (Page 46)

36 Protecting an Exchange Cluster with a Like-Named Cluster
NOTE: When you bring the source cluster online, an identical network name will still be active on the target.
Because of this, when the source cluster tries to bring up the EVS on the source, the network name resource will
fail and consequently the group will not come online on the source. You should allow the source cluster to finish
trying to bring the resources online before using the Application Manager to failback.