How to develop addin for MS Outlook?

How do I develop addin for MS Outlook that works with all 1. Outlook 2010 2. Outlook 2007 3. Outlook 2003

I have developed addin that works well with 2010 and 2007 BUT NOT with 2003.

I want something like this that works well with all the above three :)

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How Outlook Add-Ins work?

The Add-In is a little bit like an App that runs inside of Outlook. The features of the Add-In typically read some information from the email and make that information available to your main application. This is usually accomplished by your main application presenting some kind of REST API to accept the mail data.

You need VSTO (Visual Studio Tools for Office). Here is an article to get you started.

You can also check out Office Development Center.