MAPI (Messaging Application Program Interface)

Introduction: MAPI (Messaging Application Program Interface) is a Microsoft Windows program interface that enables you to send e-mail from within a Windows application and attach the document you are working on to the e-mail note.

It is a messaging architecture and a Component Object Model based API for Microsoft Windows. While MAPI is designed to be independent of the protocol, it is usually used with MAPI/RPC, the proprietary protocol that Microsoft Outlook uses to communicate with Microsoft Exchange.

MAPI was originally designed by Microsoft. The company founded its MS Mail team in 1987, but it was not until it acquired Consumers Software in 1991 to obtain Network Courier that it had a messaging product. Reworked, it was sold as MS PC Mail (or Microsoft Mail for PC Networking). The basic API to MS PC Mail was known as MAPI version 0 (or MAPI0). MAPI uses functions loosely based on the X.400 XAPIA standard.

Architecture: MAPI consists of a standard set of C language functions that are stored in a program library known as a dynamic link library (DLL). Developers who are using Microsoft's Active Server Page (ASP) technology access the MAPI library by using Microsoft's Collaboration Data Objects (CDO). The CDO library comes with Microsoft's Internet Information Server (IIS). MAPI functions can be accessed by Visual Basic developers through a Basic-to-C translation layer.

Simple MAPI is a subset of 12 functions which enable developers to add basic messaging functionality. Extended MAPI allows complete control over the messaging system on the client computer, creation and management of messages, management of the client mailbox, service providers, and so forth. Simple MAPI ships with Microsoft Windows as part of Outlook Express/Windows Mail while the full Extended MAPI ships with Office Outlook and Exchange.

In addition to the Extended MAPI client interface, programming calls can be made indirectly through the Simple MAPI API client interface, through the Common Messaging Calls (CMC) API client interface, or by the object-based CDO Library interface. These three methods are easier to use and designed for less complex messaging-enabled and -aware applications.

MAPI includes facilities to access message transports, message stores, and directories.

Applications of MAPI: Applications that take advantage of MAPI include word processors, spreadsheets, and graphics applications. MAPI-compatible applications typically include a Send Mail or Send in the File pulldown menu of the application. Selecting one of these sends a request to a MAPI server.

Eudora, one of the most popular e-mail programs, includes a MAPI server

Service Provider Interface for MAPI:  The full Extended MAPI interface is required for interfacing messaging-based services to client applications such as Outlook. For example, several non-Microsoft e-mail server product vendors created "MAPI service providers" to allow their products to be accessed via Outlook. Notable examples include Axigen Mail Server, Kerio Mailserver, Scalix, Zimbra, HP OpenMail, IBM Lotus Notes, Zarafa, and Bynari.

MAPI0 also had a service provider interface of sorts. Indeed, Microsoft used this to interface MS Mail to an email system based on Xenix, for internal use.

Extended MAPI is the main e-mail data access method used by Outlook, to interface to Microsoft Exchange, via MAPI service providers shipped with Outlook.

MAPI/RPC protocol details:   Microsoft has released full details of the MAPI/RPC protocol.

"MAPI protocol" is a colloquial name for the MAPI/RPC. At times, Microsoft has also called it "Exchange RPC" and "Outlook-Exchange Transport Protocol".