The ports of some models of manageable servers use the Advanced Lights Out Manager (ALOM) standard. These servers, detailed in Manageable Server Requirements in Sun N1 System Manager 1.3 Site Preparation Guide, use email instead of SNMP traps to send notifications about hardware events to the management server. For information about other events, see Managing Event Log Entries in Sun N1 System Manager 1.3 Discovery and Administration Guide and Setting Up Event Notifications in Sun N1 System Manager 1.3 Discovery and Administration Guide.
If there are no notifications about hardware events from ALOM architecture manageable servers, it could mean that all managed servers are all healthy. If you are using an external mail service instead of the internal secure N1 System Manager mail service, it is possible that the external mail service has not been configured correctly as an email server, or that email configuration has been invalidated due to other issues such as network error or domain name change.
To resolve, either:
Reconfigure the N1 System Manager by running n1smconfig, and choose the secure internal N1 System Manager mail service.
Check and reset your external email server configuration. See Resetting Email Accounts for ALOM-based Managed Servers