In addition to regular tasks, Google provides Google Vault product which adds archiving and eDiscovery to your Google Apps system.
It’s purpose is to manage, search, retain and export organization’s email and chat. Vault costs an additional $5 per user, per month.
In Vault, you can define retention policies that are automatically applied to your email and chat messages. Also, you can place legal holds on users if needed and run audit reports on user activity in the archive.
Use Google’s powerful algorithms for searching and find your data fast. You can retrieve information even from closed accounts, preventing data loss from employee turnover. You can export your information easily as well as audit reports for keeping track on user activities within Vault.