This section describe logging and debugging keywords.
The MTA provides facilities for logging each message as it is enqueued and dequeued. The logging and nologging keywords control logging for messages on a per-channel basis. By default, the initial configuration turns on logging for all channels. You can disable logging for a particular channel by substituting the nologging keyword in the channel definition.
logheader overrides the LOG_HEADER MTA option on a per channel basis. A value of 0 (the default) disables message header logging. See the Option File in Sun Java System Messaging Server 6.3 Administration Reference for more information.
For more information about logging, see Chapter 25, Managing Logging.
Some channel programs include optional code to assist in debugging by producing additional diagnostic output. Two channel keywords are provided to enable generation of this debugging output on a per-channel basis. The keywords are master_debug, which enables debugging output in master programs, and slave_debug, which enables debugging output in slave programs. Both types of debugging output are disabled by default, corresponding to nomaster_debug and noslave_debug.
When activated, debugging output ends up in the log file associated with the channel program. The location of the log file may vary from program to program. Log files are usually kept in the log directory. Master programs usually have log file names of the form x_master.log, where x is the name of the channel. Slave programs usually have log file names of the form x_slave.log.
On UNIX, when master_debug and slave_debug are enabled for the l channel, users then receive imta_sendmail.log-uniqueid files in their current directory (if they have write access to the directory; otherwise, the debug output goes to stdout.) containing MTA debug information.
The loopcheck keyword places a string into the SMTP EHLO response banner in order for the MTA to check if it is communicating with itself. When loopcheck is set, the SMTP server advertises an XLOOP extension.
When it communicates with an SMTP server supporting XLOOP, the MTA’s SMTP client compares the advertised string with the value of its MTA and immediately bounce the message if the client is in fact communicating with the SMTP server.