Management has determined that there is a need to search all 1500+ users Outlook and see who has been sending email to the competition. Does anybody know a tool/script/package that will enable us to search users pst files and see who has been corresponding with the enemy?
SnapOverflow
Check out Sherpa Software's products; they have some automated tools that can inventory and search PSTs on network shares or individual workstations.
When I've had to do this in the past, I used Discovery Attender. I'm assuming you have an Exchange server. They also have an option for Lotus Notes.
If it's happened recently, you could try using the Message Tracking tool in ESM. Just put in your exchange server(s) and the domain that you want to look for. Might give you clues so you don't have to search all 1500+ users' pst files.
You really need to implement an email archiving solution. Red Gate software has one (disclaimer: I've received money from them for writing articles in a magazine they publish), but Global Relay is a solid service that you can outsource it to, if you don't have the high availability stuff it requires.
An Exchange environment but with PST files? You might be able to exmerge them into a database, which will at least take some of the pain away.