There are many other options which are not required for a standard configuration. In Service Network options, the Bind to address and Port number options allow to force the daemon to listen to a specific address-and-port couple. If you have many network interfaces and you want mail traffic to pass only through a specific one, you can specify it here by entering the the interface's IP address.

In the second table named Service program options, you can redirect all your requests to another computer. In Service handled by, check Redirect to host and enter the IP address and port of the machine. The Run as user and Run as group options both allow the service to be run as a specific user.

Xinetd allows to set up boundary options for each services. The Max concurrent servers option specifies the maximum number of daemon instances to be launched at the same time. Maximum connection per second specifies the number of connection requests the server can handle. If the maximum is reached, then the Delay if maximum is reached option specifies the time interval until the instance of the service daemon will be reachable again. In the POP3 example, you can specify that only three POP3 servers can be launched and respond to five connection requests per second.

The last useful option is Nice level for server, which indicates the program's system priority.

For very large mail servers, you can use stand-alone pop-imap (not managed by xinetd).