Sun Java System Messaging Server 6.3 Administration Guide To Monitor Inbound SMTP Connections

Local address       Remote address                                 State    32768   0  32768   0   CLOSE_WAIT    8760   0  24820   0   ESTABLISHED   33580   0  24820   0   TIME_WAIT

Note that you will first need to determine the appropriate number of SMTP connections and their states (ESTABLISHED, CLOSE_WAIT, etc.) for your system to determine if a particular reading is out of the ordinary.

If you find many connections staying in the SYN_RECEIVED state this might be caused by a broken network or a denial of service attack. In addition, the lifetime of an SMTP server process is limited. This is controlled by the MTA configuration variable MAX_LIFE_TIME in the dispatcher.cnf file. The default is 86,400 seconds (one day). Similarly, MAX_LIFE_CONNS specifies the maximum number of connections a server process can handle in its lifetime. If you find a particular SMTP server that has around for a long time you may wish to investigate.