What is a COM Add-in?
COM add-ins are a feature in Microsoft Office and are supported by all Office programs, including Outlook.
Key benefits of COM add-ins include:
COM add-ins run in-process with the host program, so custom code generally runs faster than code implemented in Visual Basic for Applications.
The basic COM add-in architecture is consistent across all Office programs, whereas in previous versions of Office, each program had its own add-in architecture.
You can create one COM add-in to use with more than one Office program.
What You Need to Create a COM Add-in?
In addition to Outlook, you need one of the following development environments to create a COM add-in for Office or Outlook:
Visual Basic 5.0 or later (Visual Basic 6.0 is preferred)
Microsoft Office Developer, which includes the ability to compile a Visual Basic for Applications project into a Dynamic Link Library (DLL)
Any other COM-compliant development environment, such as Microsoft C++ or Microsoft J++