Microsoft KB Archive/177850

= INFO: What is the Difference Between CDO 1.2 and CDONTS? =

Article ID: 177850

Article Last Modified on 3/21/2005

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APPLIES TO


 * Microsoft Collaboration Data Objects 1.21
 * Microsoft Collaboration Data Objects 1.2

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This article was previously published under Q177850



SUMMARY
Collaboration Data Objects (CDO) allows developers to build collaborative applications. Currently, there are two versions of CDO. CDO version 1.2 and 1.21 for Exchange and CDO version 1.2 for Microsoft Windows NT Server (NTS). This document describes each library and helps the developer determine which is best suited to their objective.



CDO version 1.2 for Exchange
CDO version 1.2 for Exchange, replaces Active Messaging 1.1. CDO 1.2 is currently installed when you install Exchange 5.5 server or the Outlook Web Access component found on the Exchange 5.5 server CD. CDO 1.21 library is installed with Microsoft Outlook 98 Corporate Workgroup installation. It can also be installed by means of Microsoft Outlook 2000 custom installation. Please note that Microsoft Outlook 2000 standard installation does not install the CDO library.

For additional information about where to acquire CDO libraries, please refer to the article number below to view the article in the Microsoft Knowledge Base:

171440 INFO: Where to Acquire the Collaboration Data Objects Libraries

NOTE: If you install Exchange 5.5 or Outlook Web Access and then install Outlook 8.03, CDO 1.2 will be replaced with Active Messaging 1.1. See below under "Registering CDO 1.2" for more information.

CDO 1.2 for Exchange is based on MAPI and allows you to develop rich applications based on Exchange data. CDO 1.2 for Exchange contains two rich components, CDO and CDO Rendering. CDO allows you to manipulate Exchange data and to send and receive messages while CDO Rendering allows you to render Exchange data into HTML. Outlook Web Access is an excellent example of an application that takes advantage of both feature sets of CDO and is available on the Exchange server CD. Outlook Web Access allows users to view their Exchange Inbox and other folders from a Web browser.

CDO 1.2 for Exchange allows developers to build rich collaborative applications using Exchange-only features. Developers must specify or build a MAPI profile for a user to logon. This allows the user to be fully authenticated and increases the overall security. When using Active Server Pages (ASP), Internet Information Server (IIS) can impersonate the user allowing remote users to view their Exchange server information. Other key features include the ability to filter and sort messages, schedule meeting requests and add appointments, and render messages and personal calendars into HTML.

CDO 1.2 for NTS
CDO version 1.2 for NTS, also known as CDO for NTS, is an SMTP-specific lightweight version of CDO 1.2 for Exchange. This version of CDO was designed to allow server applications to send and receive messages without requiring Exchange server. CDO for NTS is installed by the following three products:
 * Exchange Server 5.5
 * Internet Information Server 4.0
 * MCIS

Applications written using CDO for NTS must run on the server computer. Unlike CDO 1.2 for Exchange, applications cannot be written to access remote servers or to develop client applications. All of the configuration information such as SMTP server is gathered from the host computer. This configuration cannot be modified using the library. Since one of the three programs is required to use CDO for NTS, there is no standalone setup program.

CDO for NTS was designed to be lightweight and to take advantage of Internet standards. To support the majority of Internet developers, a new object is available with the CDO for NTS library, called NewMail. This allows a developer to send messages using as little as four lines of code. This also allows you to send rich messages using HTML and MHTML.

Applications that are developed using the CDO for NTS library on one platform continue to work unmodified on the other platforms. For example, applications developed using Internet Information Server (IIS) version 4.0 continue to work after upgrading to Exchange 5.5.

Applications can also be upgraded to CDO 1.2 for Exchange, but some changes to the application are required. The most notable change is the ProgId and the logon information.

Comparison
Both libraries have key benefits and learning the differences between each library helps you to determine which library to use.                                       CDO 1.2 for Exchange   CDO for NTS ---

Installed with Outlook 8.03              No              No

Installed with Outlook 98                Yes             No

Installed with Exchange 5.5              Yes             Yes

Installed with IIS 4.0                   No              Yes

Installed with MCIS                      No              Yes

Callable from ASP                        Yes             Yes

MAPI based with support for profiles     Yes             No

Authenticated users and higher security  Yes             No

Access multiple remote Exchange servers  Yes             No

Access personal calendar information and other Exchange only features like Out of Office, filtering and sorting     Yes             No

Render messages and calendars into HTML  Yes             No

Compatible with Active Messaging 1.1 Applications                             Yes             No*

NewMail Object allowing mail to be sent with four lines of code                  No              Yes

HTML and MHTML support for messages with rich text and graphics                   No              Yes

Native SMTP support                      No              Yes

Compatible with IIS 4.0, Exchange 5.5 and MCIS                                 No              Yes
 * Some modifications to Active Messaging applications may be required to work with CDO for NTS and some features may not be available.

Recommended Usage
CDO 1.2 for Exchange:
 * Requires Authenticated user support
 * Rendering Exchange Data
 * Accessing personal calendar store
 * Accessing multiple remote Exchange servers
 * Accessing mail from remote sites
 * Server-based custom mail agents
 * Automatic load balancing of outgoing mail
 * Upgrading existing Active Messaging application
 * Developing client applications
 * Developing server applications
 * Filtering and Sorting messages
 * Support for multiple providers
 * Developing three tier Web-based mail applications

CDO for NTS:
 * Requires HTML or MHTML Support
 * Heavy outgoing mail processing
 * Sending unauthenticated mail from Web sites
 * Server-based replication
 * Server mail-based notification
 * Server-based custom mail agents
 * Developing server applications

Registering CDO 1.2
If Outlook 8.03 or previous is installed after CDO 1.2 is installed, CDO will be replaced with Active Messaging. This can be corrected by re- registering the Cdo.dll using the Regsvr32.exe program. Here's an example:  Select Run from the Windows Start menu.  Enter the following command: REGSVR32 CDO.DLL A dialog box should appear indicating the .dll file has been registered successfully. 

