INFO: What is the Difference Between CDO and CDONTS?

• Collaboration Data Objects (CDO), version 1.2

SUMMARY

Collaboration Data Objects (CDO) allows developers to build collaborative applications. Currently, there are two versions of CDO. CDO version 1.2 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.

MORE INFORMATION

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. Outlook version 8.03 continues to install Active Messaging 1.1.

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 for Exchange is based on MAPI and allows you to develop rich applications based on Exchange data. CDO 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 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.

Installing CDO 1.2 for Exchange on Client Computers

CDO version 1.2 is not installed by Outlook 8.03 because the library was only tested to work with server computers. While the .dll file and supporting files can be copied to a client computer and registered, this is currently not a supported configuration. Microsoft is currently testing the library for use on client computers.

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 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

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 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 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

Recommended Usage

CDO 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

• 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:

1. Select Run from the Windows Start menu.

2. Enter the following command:

         REGSVR32 CDO.DLL
   

   A dialog should appear indicating the .dll file has been registered successfully.

REFERENCES

The CDO 1.2 Help File includes documentation on CDO for Exchange and CDO for NTS.