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MAPI = Messaging Application Programming Interface, the heart of Microsoft's messaging programs. Extended MAPI serves three main purposes: 

  • It's the programming interface used to write components that connect to different mail servers, provide access to custom address books and provide rich storage facilities -- in other words, the components that you can add through see on the Tools | Services dialog in Outlook. 
  • You can use MAPI to develop new types of custom forms, not based on the built-in Outlook forms. 
  • You can create addins for Outlook, Exchange and Windows Messaging that extend the functionality of those clients. 

This is an advanced environment, mainly for C++ and Delphi developers. 

As Outlook COM add-in developers have painfully learned with the release of Office 2002 Service Pack 2, which blocks the HTMLBody property, Extended MAPI offers no direct way of extracting the HTML content from all messages. As developer Michael Schacter explains (thanks!):

HTML messages in personal folders in Outlook 2000/IMO and in Outlook 2003 have an Extended MAPI property known as PR_BODY_HTML (0x1013001E) or PR_HTML (0x10130102). One is of type PT_STRING8 and the other is PT_BINARY; otherwise they return the same information: the native message HTML.

In Outlook 2000/CW and in Outlook 2002, there is no corresponding property stored in incoming e-mails on personal folders. (It appears that incoming messages on HTTP folders (like Hotmail) and on IMAP folders, do store the PR_BODY_HTML property.) Instead, the HTML is encapsulated in RTF and stored as compressed RTF. A call to MailItem.HTMLBody converts the RTF to HTML on the fly. This is accomplished through RTFHTML.DLL, the functions of which are--to my knowledge--undocumented.

 There is a hack (in the best sense of the term) for converting RTF to HTML. However, it is not a very satisfying solution. In the sample code, search for "In actual fact" to see the beginning of the example.

MAPI SDK | What MAPI Can Do That Outlook Can't | Discussion | Samples | Tools | Problems | More Information


For advanced designers, the Microsoft Developer Network offers many online resources and examples of programming with the MAPI SDK. See:

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What MAPI Can Do That Outlook Can't

We thought it might be helpful to list some of the things that you can do with MAPI that you cannot do with the Outlook or CDO programming models. This list came from discussions with MAPI developers, a review of the SDK and samples at MSDN, and other resources listed on this page: 
  • Add commands to the toolbars and menus in Outlook 97 and 98 (but not the right-click context menu)
  • Create and update MAPI profiles
  • Create new IPM.* forms that do not use one of the built-in Outlook forms as a base
  • Track the progress of print jobs
  • Handle selected items in a view in Outlook 97 and 98
  • Export and restore views
  • Add new functionality to the Advanced Find feature via the Advanced button
  • Adding tabs to the Tools | Options and folder Properties dialogs in Outlook 97 and 98
  • Notifications beyond the application-level events exposed in the Outlook 2000 object model
  • Improved performance -- up to 50 or 100 times better performance for some operations over multiple items
  • Add a custom pane to the folder view window
  • Save an attached OLE object; see OL2002 You Receive the Cannot Save the Attachments Error Message When You Try to Use the OnWrite Extension Event for sample code
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Note: We haven't been able to find the source code downloads for all of the above samples, although some may be in the Exchange 5.5 SDK Final Version

MAPI Profiles:

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Exchange Inspector Free tool for examining the MAPI properties of items in Exchange mailboxes and public folders and in the Global Address List. Triggers Outlook security prompts.
MAPI33 .NET wrapper around Extended MAPI.
MAPI Explorer Explore the internal structure of the various objects components of persistent MAPI data.
MAPIProp Free COM component designed to read MAPI-properties of CDO and Outlook Object Model objects for Microsoft Outlook 2000, 2002/XP, 2003 without triggering security prompts. Microsoft Visual C++ 6.0 source code included.
MAPI Toolkit Library for simplifying the task of creating applications, especially MAPI service providers, that interact with the Microsoft Messaging API system library. Free.
MAPIViewer Provides an Explorer-like interface for browsing MAPI stores and viewing items and their properties. Free.
MDBViewer MAPI property and object viewer included with Exchange Server.
Outlook Spy Developer utility for finding out what's going on inside Outlook, via the Outlook object model, CDO and MAPI. You can edit and delete most properties, drag properties from one item to another, copy values to the clipboard, run scripts, monitor events.
RAPWare Easy MAPI Developer toolkit for Delphi for partial use of Extended MAPI interfaces (for example, to send messages without triggering Outlook Email Security Update prompts).
Visual MAPI Automatic code generator for MAPI (i.e. CDO) projects in Visual Basic or VBA. Donationware. Requires the VB 6.0 runtime. 
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Known problems (general):

Outlook 2003 issues:

Outlook 2002 uses a different design for connecting to MAPI transports. Therefore, some third-party MAPI transports may not work as expected. See:

Outlook 2002 issues, many fixed in Office XP Service Pack 1):

Outlook 2002 issues fixed in SP3:

Outlook 2000:

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