Microsoft Exchange Server includes the following four information stores, all of which are implementations of MAPI message stores:
The public information store contains public folders and messages that can be shared among multiple users and applications. A single public store is shared by all users within a Microsoft Exchange Server organization, even if multiple servers are used. The public information store is accessed similarly to any other MAPI store, using MAPI methods to perform most functions. However, some parameters to these methods differ from those used in other MAPI providers.
The private information store consists of mailboxes that can belong to users or to applications. Mailboxes reside at the server running Microsoft Exchange Server. With the Microsoft Exchange Client, each newly-created mailbox has four visible default folders (Deleted Items, Inbox, Outbox, and Sent Items) and several other folders that are not visible (used for storing information).
The personal folder store is part of the Microsoft Exchange Client, resides at the client computer, and is used to store items that are owned by individuals and not shared by multiple users. Personal folders can also be designated as the delivery location for mail if a user wants to store e-mail messages locally. Mail delivered to personal folders is still funneled through the mailbox on the server running Microsoft Exchange Server, but is stored wherever the personal folders are located.
The offline information store contains synchronized copies of selected folders and is created only when the user synchronizes these folders for offline access using local replication.
The message transfer agent (MTA) provides the addressing and routing information for sending messages and distributing information through the system. The MTA is the engine for routing and transferring data between Microsoft Exchange Server systems or between a Microsoft Exchange Server system and a foreign system. Each MTA is associated with one information store. The Microsoft Exchange Server MTA conforms to the 1988 X.400 Specification.
For detailed information about information stores, see the Microsoft Exchange Server documentation in the "Database and Messaging Services" section of the Microsoft Platform SDK.