Source : Free On-Line Dictionary of Computing

Messaging Application Programming Interface
     
         (MAPI) A messaging architecture and a {client}
        interface component for applications such as {electronic
        mail}, scheduling, calendaring and document management.  As a
        messaging architecture, MAPI provides a consistent interface
        for multiple {application programs} to interact with multiple
        messaging systems across a variety of {hardware} {platforms}.
     
        MAPI provides better performance and control than {Simple
        MAPI}, {Common Messaging Calls} (CMC) or the {Active Messaging
        Library}.  It has a comprehensive, open, dual-purpose
        interface, integrated with {Microsoft Windows}.  MAPI can be
        used by all levels and types of client application and
        "service providers" - driver-like components that provide a
        MAPI interface to a specific messaging system.  For example, a
        {word processor} can send documents and a {workgroup}
        application can share and store different types of data using
        MAPI.
     
        MAPI separates the programming interfaces used by the client
        applications and the service providers.  Every component works
        with a common, {Microsoft Windows}-based user interface.  For
        example, a single messaging client application can be used to
        receive messages from {fax}, a {bulletin board} system, a
        host-based messaging system and a {LAN}-based system.
        Messages from all of these systems can be delivered to a
        single "universal Inbox".
     
        MAPI is aimed at the powerful, new market of workgroup
        applications that communicate with such different messaging
        systems as fax, {DEC} {All-In-1}, {voice mail} and public
        communications services such as {AT&T} Easylink Services,
        {CompuServe} and {MCI} MAIL.  Because workgroup applications
        demand more of their messaging systems, MAPI offers much more
        than basic messaging in the programming interface and supports
        more than {local area network} (LAN)-based messaging systems.
        Applications can, for example, format text for a single
        message with a variety of fonts and present to their users a
        customised view of messages that have been filtered, sorted or
        preprocessed.
     
        MAPI is built into {Windows 95} and {Windows NT} and can be
        used by 16-bit and 32-bit Windows applications.  The
        programming interface and subsystem contained in the MAPI
        {DLL} provide objects which conform to the {Component Object
        Model}.  MAPI includes standard messaging client applications
        that demonstrate different levels of messaging support.
     
        MAPI provides cross platform support through such industry
        standards as {SMTP}, {X.400} and Common Messaging Calls.  MAPI
        is the messaging component of {Windows Open Services
        Architecture} (WOSA).
     
        [Correct expansion?  Relatonship with Microsoft?]
     
        (1997-12-03)