What is Subject Auditing and how does it work?
Subject Logging is only available in Exchange 2000/2003 and must be enabled on each Exchange Server under Server Properties on the General Tab. Once this has been enabled, along with Message Tracking, MessageStats is capable of gathering Subject Line info by either enabling Mailbox or Message Subject Auditing in the Console under the Tools Menu, Audit selecting either Mailboxes or Message Subject. Quest recommends using Mailbox Auditing because it will log all messages with subject lines included. If you've had the Subject Line enabled on the Exchange Servers for a while and still have the tracking logs, you can Interactively gather this info in MessageStats.
Please be aware that when Mailbox Auditing is enabled, the database will grow greatly. As long as SQL 2000 is being used and there is a lot of hard drive space available where the MessageStats database files reside, you shouldn't have any issues. Check the database size in the Database Maintenance Utility, under the Tools Menu in the Console, and try one or two mailboxes first. Then after a day or two, check the database size again to see how much it grew. The report to run after a gathering has successfully ran is under Mailboxes - Mailbox Auditing.