The address book in the SAP MAPI stores addresses which are frequently used. Typical Workplace users communicate with a small subset of other users, usually about 100-200 people. As a result, downloading the entire R/3 user database to the local machine would be a waste of both time and hard drive space. This, however, leaves the problem of how to keep the data on the local PC up-to-date.

For this reason, SAP MAPI constructs a new user-specific address book. This does not mean that users must insert each address individually. Instead, the address book adds recipient addresses while you work with your messages. When creating a new message, users enter the recipient address in the recipient fields To: and Cc: When the message is sent, a search is made for the recipient character string in the local address book. If the recipient is not found, the search is expanded to include the entire R/3 user database.

Users can also configure the address book themselves. For example, users can specify whether each new recipient address should be entered in the address book immediately or whether the entry should first be confirmed via a dialog box.