Having worked as an IT Director, I know the frustration of having to go through former employee email looking for important info. Also, there may have been great ideas being batted about between colleagues that never saw the light of day.
GrexIt offers a solution to those issues. GrexIt allows emails to be searched almost like a knowledge base to use for a number of different reasons. You can add selected emails to GrexIt or even forward an email to a GrexIt account to have it stored.
This video describes the tool: