V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

MAPI
       Messaging Application Program Interface (MS, WOSA, API)


The Free On-line Dictionary of Computing (30 December 2018):

Messaging Application Programming Interface
Mail Application Programming Interface
MAPI
Messaging Applications Programming Interface
Microsoft Mail Application Program 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)