I recently completed a whitepaper for HP ArcSight that details the available logs in Microsoft Exchange and how you can connect those to HP ArcSight. 

Even if you are not an ArcSight user you will still want to read this to see which logs are available for auditing in Exchange since our LOGbinder EX application will be able to get these logs in to any SIEM; not just ArcSight.

Click here to read the whitepaper.