I hope you have a working Postfix mail server and just want to see the subject line in the logs. By default postfix enables the ‘from’ and ‘to’ email addresses to be logged but it is possible to capture many useful information in the logs to help administrators or marketing campaign specialists to monitor it in real-time.
'/etc/postfix/main.cf' file with the editor of your choice and add the line
header_checks = regexp:/etc/postfix/header_checks.
Don’t forget to save it.
Append the line
/^Subject:/ WARN in the file
Now it’s time to run postmap
Restart the postfix server using the command:
Now monitor the flow of subject included in the logs using
tail -f /var/log/mail.log