The Mailbox object represents a Microsoft Exchange client that uses the Microsoft Exchange Server information store as its mail repository. A mailbox object inherits from a Mail-Recipient object, which means that it can also be contained within a Distribution-List object.
For example, a recipient who uses the POP3 protocol (Post Office protocol 3) to connect to Microsoft Exchange Server and retrieve mail must have a mailbox. Similarly, a recipient who uses a Microsoft Exchange client to connect to Microsoft Exchange Server and retrieve mail must also have a mailbox. However, LDAP and NNTP clients communicate directly with the Microsoft Exchange Server directory and are not necessarily represented by mailboxes.
Because Mailbox objects appear to MAPI as messaging user objects, use the MAPI IMailUser interface to access a Mailbox object.
For more information on accessing Mailbox objects through MAPI and through directory access functions, see Using MAPI with Directory Objects and Storing and Accessing Configuration Information.