Here is my article at Techgenix and an excerpt.
The upcoming release of Exchange Server, Exchange Server 2007, has many changes at the architectural level. These changes maximize the features available, one of them being journaling.
As a reminder, journaling is the ability to record all messages flowing in and out of an organization.
It is a very useful feature because there are many legal and regulatory requirements, such as the Sarbanes Oxley Act, SEC Rule 17A-4 and many more, that need a journaling solution.