Sun Cluster 3.1 software can only provide service for those data services that are either supplied with the Sun Cluster product or set up with the Sun Cluster data services API.
Sun Cluster software currently does not have an HA data service for the sendmail(1M) subsystem. The sendmail subsystem can run on the individual cluster nodes, but the sendmail functionality will not be highly available, including the functionality of mail delivery and mail routing, queuing, or retry.