With Exchange 2010, it has an option to create an archive mailbox for the user. This is Microsoft way of solving the PST issues, by having online archive within the Exchange system.
Creating and configuring an archive mailbox is simply and easy. You just need to check the checkbox for it during the “New Mailbox” creation under the “Archive Settings”. Check the “Create an archive mailbox for this account”
For existing users (that doesn’t have archive enabled), you can simply right-click on the user from the Exchange Management Console, and select the “Enable Archive” option.
Changing the Archive option for a user:
To change the archive option, go to the properties page of the user and select the “Archive” option under the “Mailbox Settings”