Now that Oracle comes along and it already has Oracle Beehive, we still do not know the fate of Sun Messaging Server. More about Oracle Beehive here.
Anyway, over the years, the only complain I received is that monitoring of Sun Messaging Server is not intuitive. Everything is via CLI (command lines).
Ideally, there will graphs and alerts and everything can be monitored via GUI.
Something like what AXIGEN Mail Server provides. The Status & Monitoring and Logging are manageable via GUI.
It'll take time for Sun Messaging Server to provide a web-based monitoring system. Maybe it might never happen at all.
For the time being, the following CLIs are helpful in my day-to-day work:
1) Monitor Messaging Server components using "immonitor-access". Health check using connection timeMonitors: LTMP, IMAP, HTTP, LDAP, SMTP
2) Monitor Statistic using "counterutil".
- Monitors: Connection Statistics
- Diskusage Statistics
- Server Response Statistics
3) Monitor MTA Channel Message Statistics using "imsimta counters -show"
4) Monitor MTA Queue Statistics usign "imsimta qm"
- "imsimta qm counters show": Shows total statistic to date.
- "imsimta qm summarize": Shows current queue statistics