Hi Wanan,
If your system is running syslogd, (which I almost sure it is - default setting). Your system has been maintaining a log file for mail operations. With RH9, you will find this file as /var/log. The log files are maintained in text files with names like maillog, maillog.1, maillog.2, maillog.3. The system should be auto cleaning old logs with logorate. You can use a text editor to read the logs.
At the bottom of the /etc/aliases file is the user who is to be emailed the sendmail report. If you uncomment the line like:
# Person who should get root's mail
#root: leland
the person entered next to root: will be emailed a daily report on email activity. In the example above, leland would receive the daily report in his email each day.
Regards,
LelandJ