You can use CDO 1.x to build discussion forums, guest books, help desk applications and much more on top of Microsoft Exchange Server 4.x, 5.0 and 5.5. There are three different flavors of the CDO 1.x libraries available at present.

• The First one is the CDONTS library, installed with the Microsoft Windows NT 4.0 Option Pack SMTP service. This library is designed to build simple bulk mailer systems. Note that CDOLive does not provide information about CDONTS. If you are looking for information about CDONTS please take look at the Microsoft Developer Network Online: Sending e-mail via ASP and CDO for NT server to find some information how to use CDONTS and Microsoft Active Server Pages. Note that you can also use CDONTS with Microsoft Exchange Server 5.5, because the SMTP protocol is used within both. For more information on how to install CDONTS on a Microsoft Exchange Server 5.5, please take a look at Microsoft Developer Network Online: Installing CDO for NTS.

• The Second one is the CDO 1.x library, installed with Microsoft Exchange Server 5.5 or Microsoft Outlook 9x/2000. You can use this library to build e-mail agents and more. Note that Microsoft Outlook 2000 does not install CDO 1.x by default. You need to include it separately. For more information about the CDO 1.x library, please take a look at Digging deeper into CDO.

• The Third one is the CDO Rendering library 1.x, installed with Microsoft Exchange Server 5.x only. The CDO Rendering library 1.x (CDOHTML.DLL) is used with Microsoft Active Server Pages applications (e. g. Microsoft Outlook Web Access) and will be installed on the Microsoft Exchange Server 5.5 computer only if the option Outlook Web Access (in Microsoft Exchange Server 5.0 it was called Active Server Components) is selected. Note that Microsoft Outlook Web Access 5.5 can be used with Microsoft Internet Information Server 3.0 and 4.0. However, it is not supported by Microsoft to run Microsoft Outlook Web Access 5.5 with Microsoft Internet Information Server 3.0.

The most current library of CDO 1.x (CDO.DLL) and the CDO Rendering library 1.x (CDOHTML.DLL) will be installed with the latest Microsoft Exchange Server 5.5 Service Pack. For a list of all versions, please take a look at All you ever wanted to know about ASP & CDO but were afraid to ask, Versions. Note that the CDO Rendering library 1.x (CDOHTML.DLL) is only available if you install Microsoft Outlook Web Access.

The CDO 1.x library can be used to build solutions, which are running on a Web site. That means that no components must be installed on a client machine. The whole application runs on top of the Microsoft Internet Information Server as a Microsoft Active Server Pages application. It supports multiple concurrent sessions (according to Microsoft ~1,000 users per server). It is a server component, so you can instantiate CDO 1.x objects through Microsoft Active Server Pages. For example, the Microsoft developers have used the CDO 1.x library to build Microsoft Outlook Web Access. For more information, please take a look at   All you ever wanted to know about ASP & CDO but were afraid to ask, CDO and ASP Basics.

The CDO Rendering library 1.x is designed for flexibility and performance. It implements HTML rendering of the CDO 1.x objects most used by client applications and it is not designed for development of service providers. It exposes a set of objects that can be used by Microsoft Internet Information Server to render CDO 1.x objects and properties into Hypertext Markup Language (HTML). The output is sent to a Web browser and is generated from objects and properties referenced in a Microsoft Active Server Page (ASP) file invoked by the browser. This process is known as HTML rendering. For more information about the CDO Rendering library 1.x , please take a look at All you ever wanted to know about ASP & CDO but were afraid to ask, CDO Rendering and ASP.

An often requested feature is to build a custom ActiveX control or COM object and using the CDO Rendering library 1.x functions inside. Unfortunately it can result in undefined behavior if the CDO HTML Rendering library 1.x is instantiated in your own custom ActiveX controls or COM objects. This is a design limitation of the current version of the CDO HTML Rendering library 1.x.

For more information about this issue please take a look at the Knowledge Base articles CDO Rendering Library Not Available Outside of ASP. It can be found at Knowledge Base Articles about CDO & Scripting and Routing.

For developers of Intranet or Internet based solutions a Frameset Design Time Control for Microsoft Visual InterDev is included on the Microsoft Exchange Server 5.5 CD-ROM which provides an easy way to add public folder content to a Web Site without writing any code. It does not provide the option to customize the views of the folder content and the items. It uses the standard Microsoft Outlook Web Access interface to display the public folder content.

For more information about the Frameset Design Time control, please take a look at All you ever wanted to know about ASP & CDO but were afraid to ask, FrameSet Design Time Control.

With Microsoft Exchange Server 5.5 Service Pack 1(or higher) a new HTML Forms Converter is supplied by Microsoft. With this form converter it is possible to convert Microsoft Outlook 9x/2000 forms to HTML forms. This form converter has some restrictions, e. g. it cannot convert the form script code and can only convert forms of the type IPM.NOTE, IPM.POST and IPM.CONTACT to HTML forms.

For more information about the Outlook HTML Form Converter, please take a look at All you ever wanted to know about ASP & CDO but were afraid to ask, Outlook HTML Form Converter.