I have Office 2003 VBA code that uses the technique described here to embed an image in an HTML message using undocumented MAPI properties and CDO 1.21.
CDO 1.21 is no longer supported, but according to MSDN, most of its functionality is now incorporated into the Outlook 2010 object model.
Where can I find a sample that embeds images in an Outlook 2010 message using the Outlook 2010 object model?
Found the answer here.
The key bits being: