The postfix-logwatch(1) utility is a Postfix MTA log parser
that produces summaries, details, and statistics regarding
the operation of Postfix.

A key feature of postfix-logwatch is its ability to produce
a very wide range of reports with data grouped and sorted as
much as possible to reduce noise and highlight patterns. Brief
summary reports provide a quick overview of general Postfix
operations and message delivery, calling out warnings that
may require attention. Detailed reports provide easy to scan,
hierarchically-arranged and organized information, with as
much or little detail as desired.

WWW: http://logreporters.sourceforge.net/