Exchange 2010 Email Archiving appears to be Microsoft’s answer to third-party products like Symantec Enterprise Vault and Iron Mountain-Mimosa Systems. Based upon what I see, it’ll be a nice advanced IT solution for clients that use their mail system like a filing cabinet. This is a great way of managing data and controlling data flow within an organization. It requires Exchange Enterprise CALs and is not quite ready for prime time in my humble view (some of the admin functions won’t be added to the Management Console until SP1 for Exchange 2010). But overall it looks great and I suspect we’ll consider it for a lot of clients in the future. Email items from your primary mailbox can be automatically offloaded to a personal Archive through established retention polices, and administrators can also import historical email data from .PST files directly into Exchange. Pretty slick and convenient.
Here is a great link regarding the matter.