The Microsoft Windows Messaging Subsystem allows Mail-Enabled Applications (MEAs) to use the transport services of a number of existing messaging systems. Applications use a standard Messaging Application Program Interface (MAPI) for access to the message store, addressing, and transport services of the underlying messaging system. Installed drivers, called service providers, which are customized for the particular messaging system, provide access, security, and translation services for the Windows Messaging Subsystem.
This document provides directions for the development of transport service providers for the Windows Messaging Subsystem.
Application writers should see the MAPI documentation for a description of how to write Mail-Enabled Applications.
The Windows Messaging Subsystem is a layered system. Applications (see diagram below) access the messaging subsystem using MAPI calls. Messaging operations are carried out in part by MAPI.DLL, which the application calls directly, and in part by the Message Spooler, a separate application. The MAPI.DLL and the Message Spooler in turn call upon the service providers to access store, transport, and addressing services.
Standard providers that are commonly installed on a user's system:
Local Message Store: storage and management of one user's mail
Personal Address Book (PAB): frequently accessed recipients