There are many scenarios in Exchange 2007 Server which requires parsing, monitoring, and analyzing Message Tracking logs. For example, in transaction log file and / or Database growth scenarios, Server got hit with spam messages, Looping message scenario, Transport queue backup scenarios, and Server performance scenarios, and many other administrative, monitoring, and troubleshooting scenarios - it absolutely becomes necessary to review and analyze Message Tracking Logs. The amount of fields and tremendous amount of data present in message tracking logs, and the amount of extremely high messaging traffic that Exchange servers process these days ( i.e. the sheer size of message tracking log files ) makes it extremely difficult, if not impossible, to analyze these message tracking logs manually. The task is further complicated when you have to review message tracing logs from multiple servers, and especially on a pretty regular basis.
Read more at source: http://msexchangeteam.com/archive/2008/02/07/448082.aspx