One of the first steps in troubleshooting the MTA is to determine where to begin the diagnosis. Depending on the problem, you might look for error messages in log files. In other situations, you might check all of the standard MTA processes, review the MTA configuration, or start and stop individual channels. Whatever approach you use, consider the following questions when troubleshooting the MTA:
Did configuration or environmental problems prevent messages from being accepted (for example, disk space or quota problems)?
Were MTA services such as the Dispatcher and the Job Controller present at the time the message entered the message queue?
Did network connectivity or routing problems cause messages to be stuck or misrouted on a remote system?
Did the problem occur before or after a message entered into the message queue?
This chapter will address these questions in the subsequent sections.