When users are not directly connected to Microsoft Exchange Server, they can still have access to the Favorites folder by using local replication. Local replication is the synchronization of folders located on the server with the offline folder store (OST). Local replication automatically copies the following items:
Offline folders include any folder that has been designated as an offline folder by the user through the client interface. incremental change synchronization is used to synchronize private information stores with the OST.
Folders designated as offline folders (either in the user’s mailbox or in the Favorites subtree) are copied to an OST file when the user requests folder synchronization for the folder. The complete folder hierarchy (the MAPI hierarchy table) is also copied, and is therefore identical when viewed by an offline application.
The offline folder can be accessed either offline or online at a given moment. When a user has made offline changes to a folder, these changes are automatically copied to the server the next time the user logs on to the system. Changes that may have occurred on the server while a user is offline are synchronized with the user’s OST only when he manually requests it.
An OST file is similar to a PST. The difference is that an OST file is RTF-aware, while a PST is not. The contents of any folder designated as an offline folder are included in the OST file, but the contents of the mailbox and other folders are not. For more information, see Working with Offline Folders and RTF-Awareness.